DCT

2:26-cv-00805

Dayal Family LLC v. Microsoft Corp

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 2:26-cv-00805, E.D. Tex., 09/10/2026
  • Venue Allegations: Plaintiff alleges venue is proper in the Eastern District of Texas because Microsoft has regular and established places of business in the district, including data centers, corporate offices, an internet "point of presence," and Microsoft Windows Store-within-a-store locations.
  • Core Dispute: Plaintiff alleges that Defendant’s Microsoft Excel spreadsheet application, specifically its LET() function, infringes patents related to a method for dynamically naming expressions within a formula where the name's scope is limited to a single cell.
  • Technical Context: The technology addresses the complexity and error-proneness of long spreadsheet formulas by creating locally-scoped variables, which aims to improve formula readability, reusability, and maintainability.
  • Key Procedural History: The complaint alleges that the inventor provided notice to Microsoft's CEO regarding the underlying provisional application on July 18, 2019, prior to Microsoft's launch of the accused LET() function. The complaint also alleges pre-suit knowledge based on citations of the patent family against Microsoft in unrelated patent prosecution matters.

Case Timeline

Date Event
2018-10-15 Priority Date for '258 and '642 Patents
2019-07-18 Inventor Letter to Microsoft CEO Regarding Provisional Application
2024-07-16 '258 Patent Issued
2025-06-13 Plaintiff's Patent Publication Cited Against Microsoft
2026-01-13 Plaintiff's Patent Cited Against Microsoft
2026-02-03 '642 Patent Issued
2026-09-10 Complaint Filed

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 12,541,642 - "Method and System for Dynamic Naming of Component Expressions Within a Formula in a Cell in a Spreadsheet Application"

  • Patent Identification: U.S. Patent No. 12,541,642, "Method and System for Dynamic Naming of Component Expressions Within a Formula in a Cell in a Spreadsheet Application," issued February 3, 2026.

The Invention Explained

  • Problem Addressed: The patent's background describes the difficulty of writing and understanding complex spreadsheet formulas, which can become long and difficult to debug (Compl. ¶22; ’642 Patent, col. 1:50-54). It also notes that while naming cells or ranges can simplify formulas, these names are typically "global," meaning they cannot be reused for different purposes in different cells, which limits flexibility when copying formulas (Compl. ¶27; ’642 Patent, col. 2:1-11).
  • The Patented Solution: The invention proposes a method for assigning a name to an expression within a formula, with the name's scope being limited to that single cell's formula (’642 Patent, abstract). This allows a user to define a sub-calculation once, give it a simple name (e.g., "x"), and reuse that name throughout the same formula, improving readability (’642 Patent, col. 2:12-18). Because the name is local, the same name can be used in other cells for different expressions without conflict, and formulas can be copied relationally (’642 Patent, Fig. 7).
  • Technical Importance: This approach allows for more compact, intuitive, and robust formulas, which improves user productivity and reduces the likelihood of errors in complex spreadsheet models Compl. ¶24

Key Claims at a Glance

  • The complaint asserts independent claims 1, 10, and 19 Compl. ¶37 Compl. ¶84 Claim 10 is asserted for direct infringement, while claims 1 (method) and 19 (system) are asserted for indirect infringement.
  • Independent Claim 10: A non-transitory computer-readable medium claim comprising program code to perform steps including:
    • Searching a formula in a first cell to find a "first unique symbol or unique combination of symbols."
    • In response, searching for an associated "first name" and "first expression."
    • "Equating" the first expression to the first name to create a "first relationship."
    • "Utilizing" the first relationship to evaluate another instance of the first name within the first cell.
    • The scope of this relationship is "limited to the first cell" and is "not usable in any other cell."
  • The complaint also asserts dependent claim 15, which adds limitations related to copying the formula to a second cell Compl. ¶73

U.S. Patent No. 12,039,258 - "Method and System for Dynamic Naming of Component Expressions Within a Formula in a Cell in a Spreadsheet Application"

  • Patent Identification: U.S. Patent No. 12,039,258, "Method and System for Dynamic Naming of Component Expressions Within a Formula in a Cell in a Spreadsheet Application," issued July 16, 2024.

The Invention Explained

  • Problem Addressed: Sharing a common specification with the ’642 patent, the ’258 patent addresses the same problems of unwieldy, error-prone spreadsheet formulas and the inflexibility of global naming conventions (Compl. ¶21; ’258 Patent, col. 1:45-68).
  • The Patented Solution: The invention describes a method for computing a formula by searching for a "symbol" that associates a name with an expression having a result, all within the formula itself (’258 Patent, claim 1). This assignment of a name to an expression is performed "in relation to the first cell and not in relation to any other cell," ensuring the assignment has "no relevance outside of the first cell" (’258 Patent, claim 1).
  • Technical Importance: This technology aims to make spreadsheet logic simpler to develop, audit, and transfer between users, particularly in complex models (Compl. ¶24; ’258 Patent, col. 2:45-54).

Key Claims at a Glance

  • The complaint asserts independent claims 1, 10, and 20 Compl. ¶112 Compl. ¶150 Claim 20 is asserted for direct infringement, while claims 1 (method) and 10 (system) are asserted for indirect infringement.
  • Independent Claim 20: A non-transitory computer-readable medium claim comprising program code to perform steps including:
    • Searching a formula in a first cell to find a "symbol" for associating a "first name" with a "first expression," with the expression having a "first result."
    • "Assigning" the first name to the first expression.
    • "Utilizing" the first expression's result to evaluate a subsequent instance of the first name to compute a "final result of the first cell."
    • The assignment has "no relevance outside of the first cell."
  • The complaint also asserts dependent claim 3, which adds limitations related to copying the formula Compl. ¶160

III. The Accused Instrumentality

Product Identification

  • Microsoft's Excel spreadsheet application, including installed desktop versions and the web-based application Compl. ¶29 Compl. ¶42

Functionality and Market Context

  • The complaint focuses on the "LET()" function within Excel Compl. ¶33 It alleges this function allows users to assign names to calculation results, and these names are only valid within the scope of the "LET()" function itself Compl. ¶68 The complaint provides a screenshot of Microsoft's documentation explaining the function's syntax as "=LET(name, name_value, calculation)", which it alleges directly maps to the patented invention Compl. ¶51 Another screenshot shows an example formula, "=LET(x, 5, SUM(x, 1))", where the name "x" is assigned the value "5" for use only within the "SUM" calculation in that same formula Compl. ¶64
  • The complaint cites Microsoft's own materials describing Excel as the "most popular desktop-based spreadsheet software" that is "widely used in business, education, and personal financial planning" Compl. ¶45

IV. Analysis of Infringement Allegations

’642 Patent Infringement Allegations

Claim Element (from Independent Claim 10) Alleged Infringing Functionality Complaint Citation Patent Citation
...searching a formula in a first cell of the plurality of cells to find a first unique symbol or unique combination of symbols Excel allegedly searches a formula to find the characters "LET" which constitute a unique symbol representing the built-in function. ¶54 col. 8:15-24
...in response to finding the first unique symbol..., searching the formula in the first cell for an associated first name and an associated first expression... After finding the "LET" symbol, Excel's "LET()" function is allegedly used to associate a first name (e.g., "filterCriteria") with a first expression (e.g., ""Fred""). ¶¶55-56 col. 8:25-50
...equating the first expression to the first name to create a first relationship The "LET()" function allegedly assigns the first name to the first expression, creating a relationship such as "filterCriteria="Fred"". ¶¶60-61 col. 8:41-44
...utilizing the first relationship to evaluate another instance of the first name in the first cell in computation of the formula but not to evaluate the first name in any other cell... The created relationship is allegedly used to evaluate another instance of the name within the same cell's formula, but this relationship has no meaning outside of the cell where the formula resides. ¶¶62-63; ¶67 col. 2:20-25
...wherein the formula contains a reference to at least one other cell...and wherein a scope of the first relationship is limited to the first cell... The "LET()" function is allegedly used with other functions that reference cell ranges (e.g., "FILTER(A2:D8,A2:A8=...)"), and the scope of the name-expression relationship created by "LET()" is limited to the cell containing it. ¶¶71-72 col. 1:49-50

’258 Patent Infringement Allegations

Claim Element (from Independent Claim 20) Alleged Infringing Functionality Complaint Citation Patent Citation
...searching at least a portion of a formula in a first cell...to find a symbol in the formula for associating a first name...with a first expression..., the first expression having a first result Excel allegedly searches a formula to find the "LET" symbol, which associates a name (e.g., "x") with an expression (e.g., "5") that has a result. ¶¶121-128; ¶133 col. 15:1-15
...assigning the first name to the first expression The "LET()" function allegedly assigns the first name to the first expression. ¶137 col. 15:30-31
...utilizing the first expression having the first result to evaluate a subsequent instance of the first name in the formula to compute a final result of the first cell The "LET()" function allegedly uses the first expression's result (e.g., the numeric value 5) to evaluate a subsequent instance of the name ("x") in a calculation ("SUM(x, 1)") to compute the cell's final result. ¶¶138-141 col. 15:32-38
...wherein assignment of the first name to the first expression having the first result is made in relation to the first cell and not in relation to any other cell...so that the assignment has no relevance outside of the first cell... The complaint quotes Microsoft's documentation stating "LET" allows "defining names inside a formula," alleging the scope is limited to the cell, making the assignment irrelevant outside of that cell. ¶¶142-145 col. 15:39-49
  • Identified Points of Contention:
    • Scope Question: A primary question for claim construction may be whether the accused "LET()" function constitutes a "symbol" as required by the claims. The patents' specifications and figures heavily feature a distinct syntax using an underscore operator (e.g., "((G1-G2)/G3)_X") to create the name-expression association (’642 Patent, Fig. 4; ’642 Patent, col. 8:18-24). The infringement analysis will likely turn on whether the term "symbol" can be construed broadly enough to read on a standard function call like "LET(...)" rather than the specific non-standard syntax emphasized in the patents.
    • Technical Question: The claims recite specific "searching," "finding," and "equating/assigning" steps. A key factual question for infringement will be whether the process by which Excel's engine parses and executes the arguments of the "LET()" function is functionally equivalent to the sequence of steps laid out in the claims.

V. Key Claim Terms for Construction

  • The Term: "symbol" / "unique symbol or unique combination of symbols"
  • Context and Importance: The definition of this term is fundamental to the infringement allegation. The Plaintiff's case hinges on the function name "LET" qualifying as the claimed "symbol." Defendant may argue that the "symbol" is a special, non-alphanumeric operator, as exemplified by the underscore-based syntax ("(expression)_Name") in the patent specification. Practitioners may focus on this term because its construction could be dispositive.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The specification states the operand "can be two sequential double underscore symbols, namely, "__" or any other symbol or combination thereof that has not been reserved" (’258 Patent, col. 8:18-22). This language suggests the "symbol" is not limited to the underscore example and could encompass other unique identifiers.
    • Evidence for a Narrower Interpretation: The specification repeatedly refers to the "operand symbol" and depicts it as a syntactic operator separating an expression from a name, rather than a function that takes the expression and name as arguments (’258 Patent, Fig. 4; '258 Patent, abstract). The flowcharts also refer to searching for a "name operand," which may suggest a specific type of operator is contemplated (’258 Patent, Fig. 3).

VI. Other Allegations

  • Indirect Infringement: The complaint alleges active inducement of infringement against Microsoft Compl. Count II Compl. Count IV The basis for inducement is twofold:
    1. Knowledge: Alleged pre-suit knowledge stems from a 2019 letter sent by the inventor to Microsoft's CEO concerning the parent provisional application and from the patents-in-suit being cited against Microsoft in unrelated patent matters Compl. ¶31 Compl. ¶32
    2. Intent: Intent to induce is alleged based on Microsoft providing extensive documentation, instructions, and examples for using the accused "LET()" function, which allegedly instructs and encourages users to perform the patented method Compl. ¶107 Compl. ¶177
  • Willful Infringement: The complaint alleges willful infringement based on the same pre-suit knowledge allegations, asserting that Microsoft "designed, developed, licensed, sold copies of, and distributed the Excel application with knowledge of the Asserted Patents" Compl. ¶183

VII. Analyst’s Conclusion: Key Questions for the Case

  • A core issue will be one of definitional scope: Can the term "symbol," which the patent specification heavily exemplifies as a unique syntactic operator like "__" in an "(expression)_Name" format, be construed to cover the function name "LET" in a standard "LET(name, expression, ...)" function call? The resolution of this claim construction dispute may determine the outcome of the infringement analysis.
  • A key evidentiary question will be one of functional equivalence: Does the operational sequence of Excel's formula parser when executing the "LET()" function—a standard function with arguments—match the claimed steps of "searching" for a symbol, then "searching" for a name and expression, and then "equating" or "assigning" them? The case may require a detailed technical comparison of the accused software's internal operations against the specific steps recited in the claims.
  • A central factual question for willfulness will be timing and knowledge: What did Microsoft know about the Dayal patent applications, and when did it know it, particularly in relation to the development and public launch of the accused "LET()" function? The evidence surrounding the 2019 letter to Microsoft's CEO will be critical to this inquiry.