Xml codification

1

I have three dynamics text :txt0,txt1,txt2 (main.fla)

I also have a class

Interfaz.as:

public class interfaz
 {
    public var entidad:XML;

    public function  llenarMuestra()
    {                
       for(var j=0;j<3;j++)
            { this["txt" + j].htmlText = value;  }
    }
  }

**
Main.fla**
miInterfaz.llenarMuestra();

ERROR: there is no txt0 property in interfaz

How can I acces txt0,txt1,txt2 from interfaz ?
thanks