I have a postmessage call which is
lngresult = PostMessage(GetTaskHwnd, WM_LBUTTONDOWN, 0&, ByVal lnglparam)

I wanted to know if postmessage have a return error. Because the above code only click the form with a handle of gettaskHwnd if it is in the top of the screen. If it is on the bottom of the screen, I the command will fail, but I have to programmed it so if it fails it will exit the subroutine and disregard the succeeding code statement.