TextField (input) com limite de chars

this.createTextField("age_txt", this.getNextHighestDepth(), 10, 10, 30, 22);
age_txt.type = "input";
age_txt.border = true;
age_txt.maxChars = 2;
age_txt.restrict = "0-9";
this.onEnterFrame = function(){
 if(age_txt.length == 2){
  trace("CHEGA")
 }
}