ActionScript 3.0 :: Changing Text From A Different Class

I have a class called Background that has a function that creates a textfield when my movie is first called:

Code:
public function MakePoint() {
var txt:TextField = new TextField();
addChild(txt);
txt.text = "Points: " + StaticValues.puzzlePoints.toString();
}

I want the text to change whenever the user does something. I have a function in another class that controls that. How do I change the text from another class? I've tried with the code below, but it doesn't work:

Code:
Background.txt.text = "Different Text"