Zooming problem

programming flash
1

Scenario: I have a movie clip(a large image that has the same size as the stage) and a button in a square that is small (150x150) . The zoom has to be like this:
I click on the button once and I have to zoom in (only once) exactly where the square is (in the center of it).
When I click the zoom button again I have to zoom out and every thing has to be like like the beginning. This is the code I have:
//declare vars
//The TweenLite classes
import gs.*;
//mouse object
var mouseListener:Object = {};
//How much you want to scale the map clip
var scale:Number = 500;
//In/out scale
var scaled_in:Boolean = false;
///org map size
orig_map_width = map._width;
orig_map_height = map._height;
orig_map_x = map._x;
orig_map_y = map._y;

//*********pan/zoom
map.onPress = function() {
///start drag map
startDrag(map);
};

map.onReleaseOutside = function() {
map.stopDrag();
};

map.onRelease = function() {
///stop drag map
map.stopDrag();

///get timmer
var clickTime:Number = getTimer();

//if double clicked auto zoom
if (clickTime-lastClickTime<700) {

    //do we want to zoom in our out
    if (scaled_in == false) {
        //trace("scale in");
        scaled_in = true;
        scale = 500;
        zoom_it();

    } else {
        //trace("scale out");
        scaled_in = false;
        scale = 100;
        ///send zoom
        TweenLite.to(map,0.5,{_xscale:scale, _yscale:scale, _x:orig_map_x, _y:orig_map_y});
    }

} else {
    ///they are panning
    map.stopDrag();
}

/////Store last click time//////////
lastClickTime = clickTime;

};

///zoom function
_global.zoom_it = function() {

//Mouse x/y position in map clip
var centerx:Number = map._xmouse;
var centery:Number = map._ymouse;

//Percentage of how far in we're in to the map clip 
var xpercent:Number = (centerx/map._width);
var ypercent:Number = (centery/map._height);

var targetx:Number = ((Stage.width/2)-(((orig_map_width*(scale/100))*xpercent)));
var targety:Number = ((Stage.height/2)-(((orig_map_height*(scale/100))*ypercent)));

trace(scale);
///is it larger then 1000 and less then 1
if (scale<1000 or scale>26) {
    trace("zooming");

    TweenLite.to(map,0.5,{_xscale:scale, _yscale:scale, _x:targetx, _y:targety});
}

};

///mouse wheel
/*mouseListener.onMouseWheel = function(delta, target) {

//trace("mouse Scroll");
///get total results of scale
scale = map._yscale+(delta*20);

//Zoom it
zoom_it();

};

Mouse.addListener(mouseListener);
*/
stop();

This is not working properly and I don’t know how to have different functionality every time I press a button.
Thank you.