A tough one about rollovers and z-index

Hi!

I have a nav-bar with rollover images in Dreamweaver. The tough part is that I also have some partly transparent png-graphics that overlap that nav-bar. I used z-index in order to get those graphics on top of the nav-bar.

The problem is that because of the z-indexed images on top of my buttons, the buttons do not work very well. In other words, the parts of my buttons that have the overlapping transparent pounding box from the png-graphics on top of them do not react to the mouse.

Is there a way you can think of that would allow me to keep transparent images on top of my rollover images and still have the rollovers function so that they react when the mouse is hovered over them (also in the spots that have the transparent box from the pngs on top)?

Any tips will be appreciated!