Potentially difficult (maybe subclassing) question...

I am making a program that requires that I respond to a button press in another program. In what way can I accomplish this??? Is there a way to subclass it if it is already running such that I will know when the message is recieved? I do not want to use loops ideally. Thank you for any help you can give. (I am relatively new to c++ API, so be very specific and include examples if at all possible, especially if it requires that I subclass the existing window)

Joe

If you are new to API, this is not a good thing to do. It involves DLL writing, cross-process subclassing, dll injection and interprocess communication. Someone here made a program that subclasses the windows start button. You might find it with a forum search.