http://www.internals.com/articles/apispy/apispy.htm
COM Hooking
API spying applications are great for monitoring Windows APIs, but their lack of support for COM interfaces makes them useless when trying to monitor OCXs and other OLE components. Fortunately, there is a way for monitoring COM interfaces under Windows. This technique was presented in the article Spying on COM Objects by Dmitri Leman, which was published on the July 1999 issue of WDJ.