The way we sometimes find a message number is by an educated guess about. To find the right message and numbers you'll need the Win32 API help. Its available on the web many times. ( can't find one right now :-?, I'll search a little more later ). It also comes with MSVC++ and many other packages.
Say you want to know if a checkbutton is checked. After some searching in the Win32 SDK you'll find that you need BM_GETCHECK. Looking at WinUser.h you'll find that this is 0x00F0 (240 decimal). Both wParam and lParam must be 0 according to my SDK.
The best way to find what message number to use is this, find CreateWindow in the Win32 SDK help file, scroll down. There you'll find a list with possible controls that you can create with CreateWindow. We are not interested in creating but how to control say a button, so click on "buttons". You are now in the part of the helpfile that talks about messages to buttons and stuff. This is a gold mine of information.
Hope this helps.
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