Nested function

Question

(1)
i want to add a listener that it will direct to a nested function if it triggered,
but later i found that i cant name the target event directly as "dragStart", so what should i type?
(2)
also, are there some ways that able to do the same tweening effect as the code below but without nesting them?
i made the tweenings play as one by one.
thz for any help
function changeImg() {
    mask1.removeEventListener(Event.ENTER_FRAME, mask1Drag);
    stage.addEventListener(MouseEvent.CLICK, dragStart);
     var maskTween1:Tween = new Tween(mask1,"width",Strong.easeInOut,1,750,1,true);     maskTween1.addEventListener(TweenEvent.MOTION_FINISH, playMaskTween2);
    function playMaskTween2(e) {         var maskTween2:Tween = new Tween(mask1,"width",Strong.easeInOut,750,1,1,true);         maskTween2.addEventListener(TweenEvent.MOTION_FINISH, playMaskTween3);
        function playMaskTween3(e) {             var maskTween3:Tween = new Tween(mask1,"width",Strong.easeInOut,1,750 - mouseX,1,true);             maskTween3.addEventListener(TweenEvent.MOTION_FINISH, dragStart);
           function dragStart(e) {                 maskTween1.stop();
                maskTween2.stop();
                maskTween3.stop();
                mask1.addEventListener(Event.ENTER_FRAME, mask1Drag);

Answer 1

variable declaration (eg, var maskTween1:Tween) doesn't define the variable.  it triggers memory allocation for that variable but nothing is assigned to that variable.  ie, that variable's value is null.  (the trace() function is single most important tool (by far) to understand actionscript.  use trace(maskTween1) to see its value after declaration and after assign a new Tween() to it.)
if(maskTween1==true) will always resolve to false.  ie, maskTween1 is never true.
for listeners that you want to remove, you usually remove them in the listener function as shown below.
  var   maskTween1:Tween
var maskTween2:Tween
var maskTween3:Tween
function changeImg() {
    mask1.removeEventListener(Event.ENTER_FRAME, mask1Drag);
    stage.addEventListener(MouseEvent.CLICK, dragStart);
      maskTween1 = new Tween(mask1,"width",Strong.easeInOut,1,750,1,true);     maskTween1.addEventListener(TweenEvent.MOTION_FINISH, playMaskTween2);
  function playMaskTween2(e) {
  maskTween1.removeEventListener(TweenEvent.MOTION_FINISH, playMaskTween2);
        maskTween2 = new Tween(mask1,"width",Strong.easeInOut,750,1,1,true);
        maskTween2.addEventListener(TweenEvent.MOTION_FINISH, playMaskTween3);    
   function playMaskTween3(e) {
    maskTween2.removeEventListener(TweenEvent.MOTION_FINISH, playMaskTween3);    
           maskTween3 = new Tween(mask1,"width",Strong.easeInOut,1,750 - mouseX,1,true);
            maskTween3.addEventListener(TweenEvent.MOTION_FINISH, dragStart);
function dragStart(e) {
   stage.removeEventListener(MouseEvent.CLICK, dragStart);
  maskTween3.removeEventListener(TweenEvent.MOTION_FINISH, dragStart);
                maskTween1.stop();
                 maskTween2.stop();
                 maskTween3.stop();
                 mask1.addEventListener(Event.ENTER_FRAME, mask1Drag);