Keyboard event problem

1

Hello,
i have a button that triggers an event (subClick)
I have added a keyboard event so that the user can press ENTER to also trigger subClick.
Here is the problem, when i publish, i get the following error whether i click the button or press enter:

TypeError: Error #1034: Type Coercion failed: cannot convert flash.display::MovieClip@3d69f601 to fl.controls.Button.

Also, for the keyboard to trigger the event, i have to press enter twice.
I don’t know if the error and the fact that i have to press enter twice are related, any clues? thanks,
Here is my code:

import fl.controls.Button;
import flash.display.Stage;

import flash.ui.Keyboard;
import flash.events.KeyboardEvent;

stage.addEventListener(KeyboardEvent.KEY_DOWN, keyDownHandler);
function keyDownHandler(event : KeyboardEvent) : void
{
if (event.keyCode == Keyboard.ENTER)
{
addEventListener(KeyboardEvent.KEY_DOWN,subClick);
}
}

submit_btn.addEventListener(MouseEvent.CLICK,subClick);