Movie clips swapping depths

on the audio section of this website (www.wideeyestudios.com/sweatersplash) there is a selection of 5 tabs that you can click to expand each one. I would like to know how to make each tab swap depth to go behind all the others when they are expanded, so that you can still see the other tabs when you have a tab expanded…any idea PLEASE HELP its taking me forever to solve this… :skull: