>I noticed that Messagebox() with a Timer parameter is kind of modeless. That is, user can click outside such Messagebox. The messagebox then hides but user cannot use the currently open form. In fact, the messagebox() with the Timer parameter appears on the Task Bar. I was wondering if it is possible to use the Timer parameter but still require user to click on Ok (or whatever) button of the messagebox() to clear it?

Try to add 4096 to the second parameter. See Undocumented MESSAGEBOX() parameter values FAQ #7665.