Use the record and playback wizard to record the game being played. Then modify the script it generates to be triggered when the Display_MouseDown event occurs. Of course that only works if your sprite and game are in exactly the same state when the mouse is clicked as they were when you started recording. To see how to handle mouse clicks, check the FAQ documents -- it's in there somewhere (I think there's a list of GameDev documentation sources in the forums here somewhere, and the FAQ I'm talking about is in there somewhere, but I don't remember off the top of my head).
