ActionScript 1/2 :: HitTest For Rectangular MC Over Irregular Shape

In my app, a user must drag and release a rectangular mc object (rectx) over an irregular shape within another mc object (irregx). There are 13 rect/irreg pairs. Each obj shares an AS2 file that checks whether rectx is over irregx, and proceeds _only_ if the check is true. The script uses hitTest, on mouse release, to grab the number (x) of the rectx being dragged and checks whether it's over irregx. Right now, the check comes back true when rectx is _anywhere_ inside irregx's bounding box whether it's over the actual image or not.

I've noticed that, when the (unpressed) mouse rolls over any irregx, it's oblivious to irregx's rectangular bounding box. It only reacts when it reaches the edge of the irregular shape inside, toggling from arrow to hand at the image edges. Since the mouse knows where the irregx image boundary is, is there a simple way to tap the mouse's 'eyesight' to verify whether rectx is over the correct irregx shape (meaning not just within the bounding box, within the shape inside it)? This can't be that hard.