Image preview on mouse over

I’m having a problem with a movieclip variable

function previewLoaded(e:Event):void
{

var previewArea:MovieClip = new MovieClip(); 
previewArea.addChild(flashmo_tn_bm);
trace(this);
trace(this.getChildByName('previewArea'));
while (previewArea.numChildren) { previewArea.removeChildAt(0); };
var flashmo_tn_bm:Bitmap = Bitmap(e.target.content);
flashmo_tn_bm.smoothing = true;
var pic_request:URLRequest = new URLRequest('fullpreviewimages/' + flashmo_tn_list[current_no].filename );
var pic_loader:Loader = new Loader();

}

This coding is located inside another movieclip because I’m trying to have a mouse over show a different preview area in another area of the flash. It’s as if the movieclip isn’t being recognized but I just can not figure out how to get it to work. I’ve been on this problem for 5 days and I would really like to get my website up and running. Any help would be amazing!