The only thing that you could do is install an input handler. It is generally a bad idea, however, to grab the mouse globally. A much better approach would really be to use IntuiMessages.
Mouse coordinates can also be obtained from the current screen.
But if you have a window, the best way is really to use IDCMP. That way you won't read mouse coordinates that are supposed to go to Workbench or other stuff that is running.
