Ok - I also thought about QueryInterface in the first place, both I can't figure out how to use it on a spefic DLL (only given the filename of a COM DLL to query the specific DLL wheter it supports the requested interface since). A short example might make my question more clear: I have an executable (MyProg.exe) and two COM DLL's (MyDllA.dll and MyDllB.dll). Both Dll's is allowed to support the requested interface (like add-ins in Developer Studio). In this sample both DLL's supports the interface called IMyInterface, with CLSID CLSID_MyInterface. How can I use QueryInterface in combination with the information above to verify that both DLL's support the interface IMyInterface? Martin Eskildsen

Hi, Can anybody tell me how to find out if a COM DLL has implemented a specific interface. All I know is the name of the DLL and the CLSID of the interface. I gues Microsfot is doing something similar when they implements add-ins to both Developer Studio and office? Martin Eskildsen