[MX 2004] Horizontal Sliding Menu with mouse position

What I’d like to achieve is a menu like the one you see on the USA Network Website.

I started to build my menu but the part I’m having problems with is the masked second level menu that slides horizontally depending on the mouse position. I took a script from some other FLA file but that won’t deliver the result I’m looking for. What I want is to divide my mask in 2 equal parts (left/right); placing the mouse on the left part would move the menu to the right and placing the mouse on the right side would move the menu to the left, exactly like the USA Network Website.

I uploaded my FLA file (menu.zip) for you guys to check it out. I’d really appreciate some help so I can move on to other things!

Thanks!