[Flash8]Help needed with slider bars and scaling

Hey there, this is the first time ive posted so i apologise if its a bit long winded.

I have a swf file that loads into my main movie, and within that swf there is a masked image that i would like to scale using zoom in and out buttons and also by using a slider bar.

However i cant find any tutorials that will allow me to combine the two.
I have used the following code for the buttons. Which seems to work ok but i would like it to be a little smoother. (using speed or some sort of easing??)

zoomPlus.onRelease = function(zoomIn) {
if (test_shirt.shirt._xscale == 400 && test_shirt.shirt._yscale == 400) {
zoomIn.enabled = false;
else {
test_shirt.shirt._xscale += 20;
test_shirt.shirt._yscale += 20;
zoomMinus.onRelease = function(zoomOut) {
if (test_shirt.shirt._xscale == 100 && test_shirt.shirt._yscale == 100) {
zoomOut.enabled = false;
} else {
test_shirt.shirt._xscale -= 20;
test_shirt.shirt._yscale -= 20;

Secondly i have a scroll bar that needs to also scale the image.

A further problem i can see cropping up is making the two of them work together.
eg. when the movieclip is resized to 50% using the buttons the slider should be in the middle of the slider bar.

I have found this code on kirupa for a slider:

this.ratio=0 ;
        ratio=Math.round(this._x*100/line._width) ;

and this code for a similar situation

Code on Frame 1 on main timeline

shape.targetWidth = shape._width;
shape.targetHeight = shape._height;
shape.onEnterFrame = function() {
    var speed = 5;
    this._width += (this.targetWidth-this._width)/speed;
    this._height += (this.targetHeight-this._height)/speed;

Code on first frame of Slider Movieclip:

handle.onPress = function() {
    this.startDrag(false, 0, 0, 400, 0);
handle.onRelease = function() {
handle.onEnterFrame = function() {
    _root.shape.targetWidth = this._x+10;
    _root.shape.targetHeight = this._x+10;

but for this code it keeps shrinking my initial object down to 10 pixels by 10 pixels…

Can anyone help me with all or any of this problem? or can anyone point me in the right direction.

Thanks in advance