Create an OnUpdateButton() for the button you want to disable. 2) Type in pCmdUI->Enable(FALSE); ( or pCmdUI->Enable(); ). 3) Place a break point on step (2). 4) Run your application in debug and start stepping. OR 1) Goto the MFC\SRC directory 2) Open BARTOOL.CPP 3) Search for CToolCmdUI::Enable You should have no problem figuring it out from there. I hoped this helped! INTP

I think the normal thing to be done in this case is running your do/while loop in a separate thread so you can handle all the messages, including toolbar notifications, from the main application thread normally. Your while loop condition should check on a global variable that is to be changed by the toolbar message to fail the condition.