Movieclip from variable

1

im trying to load a movieclip by a name passed threw a variable

var loader2:URLLoader = URLLoader(event.target);    
var sc:URLVariables = new URLVariables(loader2.data);
boxes[0].text = sc["Type1"];
temp = this.addChild(new sc["Type1"]);

sc[“Type1”] is equal to Archer
if i use
temp = this.addChild(new Archer());
it works correctly
so it isn’t a Typo

i get this error

TypeError: Error #1007: Instantiation attempted on a non-constructor.