Play tween after the content is loaded

My site is build up around the “The Best Structure for your Flash Site” tut. (Thank’s Mark!). Here’s the code I use to load my pages into it’s container.

Can anybody help me gettin the showContent-tween to play after my page is loaded?
(In other words, when getBytesLoaded == getBytesTotal.)

function buttonClick():Void { = this.linkURL;
    import mx.transitions.Tween;
    import mx.transitions.easing.*;
    var hideContent:Tween = new Tween(cone.cover, "_height", Strong.easeOut, 0, 340, 0.3, true);
    hideContent.onMotionFinished = function() {
        var showContent:Tween = new Tween(cone.cover, "_height", Strong.easeOut, 340, 0, 0.3, true);
        loadMovie(, cone.content_container);

I couldn’t figure out where and how to use it.