This command will put a Windows message on the stack so that, when it comes up in the loop, the routine named will be called.
|POSTMSG f/c/e||Required - The label you want to call. The routine must end in a RET.|
Windows is basically a list of messages. That list is constantly being updated and added to. This command brings you to that level of Windows without forcing you to deal with the complexity. Even though there are lots of different messages in Windows, this is only one. When you execute this command, a message is added that tells Windows to run a routine in your program. If the routine doesn't exist the command will do nothing. Also, you want to include this command just before you do a return.
Why is this here? Because sometimes there's no other solution. Sometimes what you want to happen won't until you return to Windows. And, if you're not done, you need some way of coming back. This is the method.