Error #1010: A term is undefined and has no properties, scope issue?

Hi, I’m having trouble getting to the bottom of this error. The debugger says my class is undefined. Wonder if you might have some ideas, I cannot manipulate the properties in side the Ball class I have created in my main document class.

May be a scope error of some kind or a problem with my Ball class declaration.

/* Main Document Class*/
package  {
import flash.geom.ColorTransform;
import flash.display.MovieClip;
import fl.motion.Color;
import flash.display.*;

//-- This class performs the animation in the main canvas. ----------
public dynamic class Main extends MovieClip {
  private var max,num,cur,mxm,mym:int = 100; // current ball and mouse x y & number of balls
  //private var Ball[] ball = new Ball[max];        // array of balls for interaction purposes
  private var massArray:Array = new Array();
  //Ticker tick;
  private var clearAll:Boolean;
  //  The following are some "physical" properties.  Each property
  //  has a value and a control.  The values are updated once per
  //  animation loop 
  public var g,mg,f,r:Number;
  public var trc,col,mu,wr,sm,fi:Boolean;
  public var xsize,ysize:int;
  //Scrollbar grav,mgrav,fric,rest;
  //Checkbox trace,collide,mush,wrap,smooth,filled;

[COLOR="RoyalBlue"]private var mass1,mass2,mass3:Ball; //  a few balls just for testing[/COLOR]
public var colorYellow:Color=new Color();
public function Main():void {
		 var myMC:MovieClip = new MovieClip();
		var _stage:Stage=myMC.stage;
		var starBackground:Stars =  new Stars(_stage);
    	//Add three balls
[COLOR="royalblue"]    	var mass1:Ball = new Ball(100,12,colorYellow,100,250,4,2,_stage,myMC); = "m1";
	 	var mass2:Ball = new Ball(100,15,colorYellow,325,225,-5.45,1,_stage,myMC); = "m2";
	  	var mass3:Ball = new Ball(100,22,colorYellow,400,50,0.45,1,_stage,myMC); = "m3";
		addEventListener(Event.ADDED_TO_STAGE, moveobj);

public function moveobj(event:Event) {

//error Error #1010: A term is undefined and has no properties
[COLOR="Red"]**mass1._x+=1**; **// error points to here**[/COLOR]

}//end function