Help with Zoom and Drag variables


Im using a modified version of the page flip engine and have set a zoom button which works perfect. The code below is to set the drag limits when the zoom is at 25%.

How would i modify this so it can determine the level of zoom and apply the correct drag values??? I have 4 levels of zoom.

pages.onMouseDown = function () {
// check if page is zoomed
if (pages._xscale != 25) {
Dragging = true;
startDrag(this,false, 950,510,590,322);

Any help would be massivley appreciated.