AS3.0 help?

Hey so heres my coding:

function setButton(mc:MovieClip, slide:int):void {
mc.addEventListener(MouseEvent.CLICK, function() { showSlide(slide); } );
mc.buttonMode = true;
}

var tweenAlphaOut:Tween, tweenAlphaIn:Tween;
var tweenXOut:Tween, tweenXIn:Tween;

function showSlide(slide:int):void {
if(slide != currentSlide)
{
tweenAlphaOut = new Tween(pageArray[currentSlide], “alpha”, Regular.easeOut,1,0,2,true);
tweenAlphaOut.addEventListener(Tween… hideMC);

//tweenXOut = new Tween(pageArray[currentSlide], “x”, Regular.easeOut,0,400,.5,true);
//pageArray[currentSlide].visible = false;
pageArray[currentSlide].enabled = false;

trace("Transition in: "+slide);
tweenAlphaIn = new Tween(pageArray[slide], “alpha”, Regular.easeOut, 0, 1, 2, true);
tweenAlphaOut.addEventListener(Tween… showMC);

//tweenXIn = new Tween(pageArray[slide], “x”, Regular.easeOut,400,0,.5,true);
pageArray[slide].visible = true;
pageArray[slide].enabled = true;

currentSlide = slide;
}
}

But I want it so that it doesnt enable a MC that I loaded before. For instance, if I loaded a MC named “a”, then i load a MC named “b”, i want “a” to be unloaded :P…HELP?