Application GUID and Secret Key

The Application GUID is used by the application to store its settings on the end user’s computer and to manage save files.

The Application Secret Key is used to create secure save files (modifications to your compiled workbook saved by customers). It ensures that secure workbook save files (.XLSC or .XLSCE extensions) made with your application can only be opened by your application and not in someone else's application.

If you update your workbook, and if you want older versions to be ignored, generate a new Application GUID. Otherwise, you should never change it.