When running a custom action to call a function from a standard dll, I see these lines:
MSI (s) (44:98) [16:30:00:880]: PROPERTY CHANGE: Adding GenerateGuid property. Its value is 'C:\Users\xxxx\AppData\Local\Temp\GenerateGuid.dll?S;USER_GUID;S;GetGuid;'.
Action ended 16:30:00: AI_DATA_SETTER_5 ...