Declare it in IDL e.g. typedef [v1_enum] enum LogLevel // These are the possible levels of log { None = 1, Error = 2, Warning = 3 }LogLevel; Use it in an interface parameter if you need to export a method: interface IMyErrors : IDispatch { HRESULT GetCurrentError(LogLevel udtLevel,... ... Compile and and export as a type library or .dll or import the IDL into a .h file

You need to include the ErrSupport.idl into your project, so that the TLB and H are created by the MIDL compiler, in order that your import statement works you may need also need to add an importlib in your library block too, if you want to marshal that interface The above is a precis of some comments in some of my code from a few years ago, with the following link, that may provide more help - http://groups.google.com.au/group/microsoft.public.vc.atl/browse_thread/thread/7ca944c27b0288f4/9e1752e6feb4972a?lnk=st&q=import+common+idl#9e1752e6feb4972a[^]