Posts a message to the main thread's message queue
BOOL PostMessage( CXllMtMsg* msg );
A message of a class descended from CXllMtMsg. The message will no longer be owned by the posting thread; it will be the responsibility of the main thread from here on.
Returns TRUE if the function succeeded, FALSE if it failed. If it failed, then the caller is reposible for deleting the message.
This function may only be called from any thread, including the main thread.