Advance to next frame of loaded swf: done, how would I reverse!?

With the help of the adobe forums, I have figured out part of my problem, however – am in a stickier situation now, and hoping I can get some info here.

Pretty much, I have loaded an external slideshow with a forward, and a backward button. Each slide has an animation “in” as well. Using the following code, when I hit the next button, the show cycles through nicely:

var labels:Array = new Array(“zero”,“one”,“two”,“three”);
function nextClick (e:MouseEvent):void{
var mc:MovieClip = MovieClip(imageLoader.content);
var nextLabel:String = labels[labels.indexOf(String(mc.currentLabel))+1];
mc.gotoAndPlay (nextLabel);

Now, I am trying to figure out a way that when I click my “back” button, the slide will go to the last frame of the previous animation, and play backwards to the previous label – is this doable, or rather – what would you suggest as the best way to do so?