Currently, the DispatchEvents 3-param/4-param constructors accept only a prog-id. It appears that not all CoClasses that support events have a prog-id. Case in point, Excel.Workbook. Doesn't exist. Of if it does, I can't find it.
It is pretty easy to find the GUID for the default event interface for a CoClass using tlbinf32.dll.
Would it be possible to have the 3-param constructor accept either a prog-id *or* the GUID to the event interface for the object?