Easy Flash Menu highlight script.

I am working on a flash site and I have a menu with a slightly trnasparent rectangle the is on the top layer. I want to animate the rectangle with actionscript to scroll over an item that is clicked. I want it to animate using actionscript and have some easy on it so the rectanlge will always reach its target in the same amount of frames. For example if its over the first item and someone clicks the last item it will go faster than if someone chooses an item thats next to the one currently selected.

Thanks in advance,
Max