Look up WM_USER in the help text. This is a #defined constant in the Windows header files that is always equal to the highest Windows message ID. Thus, you can safely define your own IDs starting at WM_USER + 1. Beware, however, that some Windows common controls use IDs above WM_USER, so what I have done use WM_USER + 1000, + 1001, + 1002, etc., and I have not had any problems. Scott