This macro maps a command message to an extended command-handler member function.
An extended form of command message handlers is available for advanced uses. The ON_COMMAND_EX macro is used for such message handlers, and it provides a superset of the ON_COMMAND functionality. Extended command-handler member functions take a single parameter, a UINT containing the command ID, and return a BOOL. The return value should be TRUE to indicate that the command has been handled; otherwise routing will continue to other command target objects.
For more information, see Technical Note TN006: Message Maps.