Changing MC Depth?

Hi peoples!

Here is my issue. I have 6 MCs that are the same size and are on the same position on the stage. I am using AC variables to activate each one of them, here is an example of my script for the button:

 on (release) {
 if (number(test) == 2) {
  test = 0;
 } else {
  test = 2;
 }
} 

What I would like to do is to make the MC that I am activating go to the top of the other MCs. Anyone know how?