Whats wrong: XML SOUND

I am trying to load in a sound from XML into a empty movieclip when a user selects a button… this is my code for loading the sound but I can’t get it to play.

function loadXML(loaded) {
 if (loaded) {
  _root.ContentSound = this.firstChild.childNodes[0].childNodes[3].firstChild.nodeValue;
//  trace(this.firstChild.childNodes[0].childNodes[3].firstChild.nodeValue);
  _root.soundplaying_mc._visible = true;
  function firstImage() {
   if (loaded == filesize) {
    picture._alpha = 0;
 } else {
  trace("file not loaded!");
xmlData = new XML();
xmlData.ignoreWhite = true;
xmlData.onLoad = loadXML;


Any ideas as to where I am goign wrong? Thanks