Disabling buttons when changing depths of movie clips

I’m working on an Flash 8, trying to produce an interactive gallery where a row of buttons along the bottom fade in correspondent movie clip by bringing them to the front and triggering the start.

All works fine, except if the same button is hit twice in a row it shows the previous movie clip positioned behind it as it reloads.

I need to be able to disable the button that loads the movie clip positioned at the front so only clips positioned on lower depths can be brought forward.

my coding for each button is as follows…

on (release) {
//Bring to Front Behavior
mx.behaviors.DepthControl.bringToFront(this.movieclipname);
//End Behavior

//Movieclip GotoAndPlay Behavior
this.*movieclipname*.gotoAndPlay("1");
//End Behavior

}

I’ve been unsuccessfully trying to but a condition in at the start that only activates the button if the clip is not at the front.

If anyone has any idea of the correct actionscript that would do this i would be very grateful to hear from you.

Thanks

Jcubb