why am I getting 1120: Access of undefined property ?

So I created this simple counter script to create a score board for a game.

import flash.events.MouseEvent;

redButton.addEventListener(MouseEvent.CLICK, randomOutput);

function randomOutput(e: MouseEvent): void {

  var count: Number = 0;

  count = count + 100;

  Counter.text = (count).toString();

}

It worked fine on the stage timeline. but when I transferred this code to ActionScript file I get the 1120 error on both redButton and Counter Instance Names. why? what am I doing wrong?

Here is the full code for the ActionScript file

package {

  import flash.display.MovieClip

  public class myScript1 extends MovieClip {

  public function myScript1() {

  // constructor code

  }

}

}

import flash.events.MouseEvent;

redButton.addEventListener(MouseEvent.CLICK, randomOutput);

function randomOutput(e: MouseEvent): void {

  var count: Number = 0;

  count = count + 100;

  Counter.text = (count).toString();

}