Microsoft Excel (Advanced) Excel Custom Functions API API for creating custom functions in Excel using JavaScript. Documentation GitHub Documentation 📖 Documentation https://learn.microsoft.com/en-us/office/dev/add-ins/excel/custom-functions-overview Other Resources 🔗 Tutorial https://learn.microsoft.com/en-us/office/dev/add-ins/tutorials/excel-tutorial-create-custom-functions 🔗 Best Practices https://learn.microsoft.com/en-us/office/dev/add-ins/excel/custom-functions-best-practices