Can't set width height

1

Hi! I’ve got a MC mcBox on the scene (_root.mcBox).


var screenW = 0;
var screenH = 0;
xml_playlist.onLoad = function(success){
    if (success){
          ....Reading XML....
        setBoxSize();
   }
}
var xml_playlist = new XML();
xml_playlist.ignoreWhite = true;
xml_playlist.load(xmlURL);

function setScreenSize(){
    mcBox._width = screenW;
    mcBox._height = screenH;
    trace("W: " + screenW + " H: " + screenH); // output: W: 800 H: 600
    trace(mcBox._width); // output: 0
}

Why the MC-width and heigth doesnt change? I just don’t understand?