display value in textfield based of dropdown list selection

I only want one value to display in a textfield based of what is selected from the dropdown field.  I also would like for the dropdown list value to display as well.

Right now, this is what I have but the user is able is able to input more than one value from the dropdown list.

if  (  QWcomm.rawValue ==null  )

QWcomm.rawValue = xfa.event.newText; else

QWcomm.rawValue += ( "\n" + xfa.event.newText );

for (var i = 5; i < this.items.nodes.length; i++ ) {

      aValue= this.resolveNode("items.#text[" + i + "]").value;

      if ( sValue === xfa.event.newText )

      {

            this .deleteItem (  i  );

            xfa.event.change = "";

            break;

      }

}