Changing the x/y position of an instance from an external .as? (AS3)

First post!

Been searching the boards/web for a couple days now looking for an answer to the following. Apologies if this has already been answered previously. And I’m new to ActionScripting in general, hence the lengthy explanation.

I have an .fla, DocumentClass.as, Ball.as and Buttons.as all in the same folder. The Document Class:

  • Creates an instance of Buttons, gives it an x/y position and adds it to the stage

The Button Class: (assigned to a MC in my library)

  • Has an event listener that listens for a mouse click
  • When clicked, the button creates an instance of Ball, gives it an x/y position and adds it to the stage (instance name is _ball)
  • Then calls a function Go(); which is in the Ball class ( e.g., _ball.Go(); )

The Ball Class: (assigned to a MC in my library)

  • The Go(); function is called successfully from the button mentioned above (traces to the output panel)

THE PROBLEM

  • I also want to Go(); function to update the position of the instance _ball, but the instance isn’t recognized within the class Ball.

(if I try _ball.x = 100 I get, 1119: Access of possibly undefined property ball through a reference with static type flash.display:Stage.)

How would one go about doing this?