duplicateMovieClip help

I having trouble duplicating my movieClip onto another movieClip called “Floor”. I can duplicate the floor movieClip but not the item I am selecting in my scrollPane. I don’t know what I am doing wrong. Can someone help?

combo_list.change = function(eventObj) {
 var selItem:Object = eventObj.target.selectedItem;
 //trace("Item selected was:  "+selItem.label);
 var itemXML:XMLNode = selItem.data;
 //use saved reference to iterate through childNodes
 for (var i = 0; i<itemXML.childNodes.length; i++) {
  //trace("Item includes: "+itemXML.childNodes[idx].attributes.Text);
  var t_mc:MovieClip;
  t_mc = thumbs.content.attachMovie("thumb_mc", "thumb"+i, i, this.getNextHighestDepth());
  t_mc._x = 5;
  t_mc._y = 5+(i*80);
  //this loads the swf into the thumbs scrollPane
  _root["mc"+idx] = new MovieClipLoader();
  _root["mc"+idx].loadClip("decals/"+itemXML.childNodes*.attributes.ItemSWF+".swf", t_mc.Container_mc);  
  t_mc.i = i;
  t_mc.piece = itemXML.childNodes*.attributes.ItemSWF;
  t_mc.onRelease = function() {   
   floor.duplicateMovieClip("piece", this.getNextHighestDepth(), {_x:200, _y:100}); 
combo_list.addEventListener("change", combo_list);