Adding easing to a scrollable image

I’m trying to add easing motion to an object that is scrollable. I’m aware of the tweenclass functions and how to use them on objects, I’m just not sure on the coding for adding it to this code. So any help would be greatly appreciated. Thanks again.

Here’s the code I’m using for the movie clip.

scrolling = function () {
 
 var scrollHeight:Number = scrollTrack._height;
 var contentHeight:Number = contentMain._height;
 var scrollFaceHeight:Number = scrollFace._height;
 var maskHeight:Number = maskedView._height;
 var initPosition:Number = scrollFace._y=scrollTrack._y;
 var initContentPos:Number = contentMain._y;
 var finalContentPos:Number = maskHeight-contentHeight+initContentPos;
 var left:Number = scrollTrack._x;
 var top:Number = scrollTrack._y;
 var right:Number = scrollTrack._x;
 var bottom:Number = scrollTrack._height-scrollFaceHeight+scrollTrack._y;
 var dy:Number = 0;
 var speed:Number = 10;
 var moveVal:Number = (contentHeight-maskHeight)/(scrollHeight-scrollFaceHeight);
  
 scrollFace.onPress = function() {
 
 var currPos:Number = this._y;
 startDrag(this, false, left, top, right, bottom);
 this.onMouseMove = function() {
 
 dy = Math.abs(initPosition-this._y);
 contentMain._y = Math.round(dy*-1*moveVal+initContentPos);
 
 };
 
 };
 scrollFace.onMouseUp = function() {
 
 stopDrag();
 delete this.onMouseMove;
 
 };
 btnUp.onPress = function() {
 
 this.onEnterFrame = function() {
 
 if (contentMain._y+speed<maskedView._y) {
 
 if (scrollFace._y<=top) {
 
 scrollFace._y = top;
 
 } else {
 
 scrollFace._y -= speed/moveVal;
 
 }
 contentMain._y += speed;
 
 } else {
 
 scrollFace._y = top;
 contentMain._y = maskedView._y;
 delete this.onEnterFrame;
 
 }
 
 };
 
 };
 btnUp.onDragOut = function() {
 
 delete this.onEnterFrame;
 
 };
 btnUp.onRollOut = function() {
 
 delete this.onEnterFrame;
 
 };
 btnDown.onPress = function() {
 
 this.onEnterFrame = function() {
 
 if (contentMain._y-speed>finalContentPos) {
 
 if (scrollFace._y>=bottom) {
 
 scrollFace._y = bottom;
 
 } else {
 
 scrollFace._y += speed/moveVal;
 
 }
 contentMain._y -= speed;
 
 } else {
 
 scrollFace._y = bottom;
 contentMain._y = finalContentPos;
 delete this.onEnterFrame;
 
 }
 
 };
 
 };
 btnDown.onRelease = function() {
 
 delete this.onEnterFrame;
 
 };
 btnDown.onDragOut = function() {
 
 delete this.onEnterFrame;
 
 };
  
 if (contentHeight<maskHeight) {
 
 scrollFace._visible = false;
 btnUp.enabled = false;
 btnDown.enabled = false;
 
 } else {
 
 scrollFace._visible = true;
 btnUp.enabled = true;
 btnDown.enabled = true;
 
 }
 
 };
 scrolling();