Calline function in Excel - No Return?

Hello,

I call a function in a excelsheet by ole like that:

COleVariant varReturn = app.Run(COleVariant(COleVariant((LPCTSTR) strMakro)), var1, covOptional, ...);

After the call the varReturn is always empty, but in the function something is returned. Also the var1 is not changed but defined as ByRef in the function.

Whats the problem?

Thanks

Michael