Pan and zoom mousewheel with bounds

Hi,

I have an image with 1500x1000 size.i have 750x500 stage then two buttons zoom in and out. Now i want to know the bounds im going to use for my image. any suggestions and tutorial will be a big help thanks a lot:I use the code below:



package
{
import flash.display.*;
import flash.net.*;
import flash.events.*;

public class Map extends Sprite
{
private var btnLoader:Loader;
private var mapLoader:Loader;

public function Map()
{
//zoom
btn_zin.addEventListener(MouseEvent.CLICK, zoomImage);
btn_zout.addEventListener(MouseEvent.CLICK, zoomImage);

//scroll
btn_up.addEventListener(MouseEvent.CLICK, panImage);
btn_down.addEventListener(MouseEvent.CLICK, panImage);
btn_left.addEventListener(MouseEvent.CLICK, panImage);
btn_right.addEventListener(MouseEvent.CLICK, panImage);

map_mc.addEventListener(MouseEvent.CLICK, onloaderComplete);

//drag
map_mc.addEventListener(MouseEvent.MOUSE_DOWN, mapStartDrag);
map_mc.addEventListener(MouseEvent.MOUSE_UP, mapStopDrag);

btnLoader = new Loader();
btnLoader.load(new URLRequest("buttons.swf"));
addChild(btnLoader);

mapLoader = new Loader();
mapLoader.load(new URLRequest("map.swf"));
addChild(mapLoader);

}

function onloaderComplete(e:Event):void
{

map_mc.addEventListener(Event.COMPLETE, onloaderComplete, false, 0, true);
trace("i was click by you");
}

public function mapStopDrag(event:MouseEvent)
{
map_mc.stopDrag();
}

public function mapStartDrag(event:MouseEvent)
{
map_mc.startDrag();
}

public function mouseWheel(event:MouseEvent)
{
map_mc.z += 500;
}

public function panImage(event:MouseEvent)
{

switch(event.target)
{
case btn_up:
map_mc.y += 100;
break;

case btn_down:
map_mc.y -= 100;
break;

case btn_left:
map_mc.x += 100;
break;

case btn_right:
map_mc.x -= 100;
break;
}
}


public function zoomImage(event:MouseEvent)
{

switch(event.target)
{
case btn_zin:
map_mc.z -= 100;
break;

case btn_zout:
map_mc.z += 100;
break;
}
}

}
}