Navigation menu in flash: how button stay down and change

Hi, everybody i am new in flash and new at this forum. Here’s my question.

I just have made a navigation menu and i would like to stay the buttons color when i click on it. While clicking onthe button called “Verhalen samenleving” this button (now green) will be red and the page linked to this button will load in the html-frame below it. When clicked on another button, the button next to it (ex. verhalen wonen) i want to change this button into red and the vehralen samenleving into the original state (green)

My files:

fla (using scenes)

I hope u people know a solution and are willing to help me.