Just for combo boxes and / or list boxes?
If you select an entry of a combobox, you get a "CBN_SELCHANGE" event and "CBN_" indicates a combobox notification.
The same applies to a listbox except that you get a "LBN_SELCHANGE" event, "LBN_" because it's a listbox notification.
You can find a list of possible listbox-notifications here:
http://msdn.microsoft.com/en-us/library/ff485968%28v=VS.85%29.aspxA list of combobox-notifications is here:
http://msdn.microsoft.com/en-us/library/ff485902%28v=VS.85%29.aspxAll notifications work by the same principle:
You'll receive a "WM_COMMAND" message with the dialog-item in the low-word of "wparam" and the event-id in the high-word.
If you're unsure how a certain event works, just put a break-point into your message-handler and have a look.