textbox OnChange in AS3.0 not work?

[DanielGianni]

txt1.addEventListener(Event.CHANGE, setText);

function setText(e:Event):void {
   txt3.text="changed";
}

but I tried and did not work, txt3 is never set as changed, see if I put txt1.Text = "test" should automatically trigger the listen but it does not happen ever. I do not know where is the problem?!