[F8] What scripting should I use?

I have designed a face model in flash so the user can place sunglasses on, the user can then undo this action and place another pair of sunglasses on.

The only problem is, when a pair of sunglasses are placed on, the user can still place other sunglasess on top of the current pair and they stack up, which looks bad.

Here is the scripting I have used, I have done the scripting for the undo button on a seperate layer to the rest of the actionscript. Basically I am using the coordinates to move the sunglasses back and from the face model and then to its previous postion.

How can I script this so the user can only place one pair of sunglasses on the model at a time?

I have attached a screenshot of the application so you can get a more clear idea.

Undo button scripting:

arnette_mc.onRelease = function(){
arnette_mc._x =81.9;
arnette_mc._y =248.5;
}
oakley_mc.onRelease = function(){
oakley_mc._x =82.3;
oakley_mc._y =253.7;
}
mauirijim_mc.onRelease = function(){
mauirijim_mc._x =79.5;
mauirijim_mc._y =254.2;
}
DG_mc.onRelease = function(){
DG_mc._x =78.5
DG_mc._y =256.1;
}
bb_mc.onRelease = function(){
bb_mc._x =78.8;
bb_mc._y =252.8;
}

Action script for placing sunglasses on the model:

arnette_mc.onRelease = function(){
arnette_mc._x =81.9;
arnette_mc._y =248.5;
}
oakley_mc.onRelease = function(){
oakley_mc._x =82.3;
oakley_mc._y =253.7;
}
mauirijim_mc.onRelease = function(){
mauirijim_mc._x =79.5;
mauirijim_mc._y =254.2;
}
DG_mc.onRelease = function(){
DG_mc._x =78.5
DG_mc._y =256.1;
}
bb_mc.onRelease = function(){
bb_mc._x =78.8;
bb_mc._y =252.8;
}