Funky bar menu help needed!

Hi!

Can anyone explain to me how i would make a sliding menu that. when an item is rolled over, a bar stretches from the right of the menu to cover the words. Then if another button is rolled over, the bar stretches to cover the words again.

Hopefully someone understood that, i’ve attached some pictures to help you understand me…

pic1 - The mouse is not over any buttons

pic 2 - The mouse is over button 1

pic 3 - The mouse is over buton 2