Hi Marcus, Are you referring to calling into a managed C++ control library used by a VB.NET application? If so, there shouldn't be much you need to know. If you are trying to create a C/C++ DLL with the same "__stdcall" calling conventions used by the Win32 API, that keyword itself should be what you need for your C++ DLL. If you can describe exactly what you need (i.e. both languages, versions, etc.) I can be of more help. Regards, Joe