JavaScript

I am working on an interface for my web page..
I need to write a JavaScript that will cause a seperate image to change when I move my mouse over a button image.. I need to define two hotspots on the button image (like an image map in html). The interface is designed such that there are three images side by side. The two outside images are for four buttons. The center image will change when the mouse moves over one of the buttons.. I would also like the button to change at the same time..I haveinvested a lot of time in the graphics and now I would love to see it work..
Thanks,
Dwayne