Silktest is supporting only standard DLLs (like kernal32.dll, user32.dll) and it is not supporting COM Dlls like which is having class concepts (like VBA Applications). Standard DLLs are developing by using C, C++, VC++. I'm not sure about c#. But you can't create Standard Dlls by using VB.

To support COM Dlls, A Wrapper could be written for the COM DLL in some other language (C, Visual Basic, WSH, etc).