XLW is a C++ wrapper for the Excel C API described in the Microsoft Excel 97 Developer's Kit. It makes xll programming automatic. Its powerful interface will empower your C, C# or C++ numerics by embedding them in Excel just like the built-in functions.
Excel/VBA Integration of Picat programming language
Picartesius is a VBA library created by Lorenz Schiffmann for integrating Picat in Excel Spreadsheets.
https://sourceforge.net/projects/picartesius
Picat is a simple, and yet powerful, logic-based multi-paradigm programming language created by Neng-Fa Zhou and Jonathan Fruhman aimed for general-purpose applications.
http://picat-lang.org