hi Aspose.cells support,
Thanks for your posting and using Aspose.Cells for .NET.
FYI: In Excel, there are two types of non built-in functions: Macro and Addin. We could not know which type is an unknown function.
So we added Cell.SetAddInFormula method and CellsHelper.AddAddInFunction() to set addin function.
As you can directly enter an AddIn by just typing it like a normal Excel formula in Excel, you do not need to call Cell.SetAddInFormula method.
Please call CellsHelper.AddAddInFunction() to initialize all your addin functions before construct the workbook instance.
Please see the following code.
Workbook workbook = new Workbook();
Worksheet ws = workbook.Worksheets;
ws.Cells[“A1”].Formula = “=FUNCTION1(A2)”