Mouse easing along horizontal line

Does anyone know of a simple way/a tutorial which could help me create the following effect:

I have a standard navigation bar. As I move my mouse over each button, I want an object eg a dot (clip) to follow the mouse (above) each button -ALONG A HORIZONTAL LINE.

The effect can be seen at http://www.b7ven.com/v2/ when the mouse rolls over any of the navigation buttons.

Thanx!

start here. Same concept.

http://www.kirupa.com/developer/actionscript/advanced.htm