Money poorly spent?

Just bought a new flash 8 action script 2.0 book and I’m going through the custom classes section.

This is Motion.as, say hello he’s only a few hours old!

class Motion extends MovieClip{
function Motion(){
trace(“Motion class instantiated”);
}
function updatePosition():Void{
this._x++;
this._y++;
}
function onEnterFrame():Void{
this.updatePosition;
}
}

When I link him from the fla file and run it’s doing the trace comment once, but it’s not doing the movement. Am I missing something.

Identifier = MotionShape
AS 2.0 class = Motion