ActionScript 3.0 :: Getting Buttons To Work With Image Transitions Through Xml

I have been trying to figure out this problem for a couple days. I made an animation using actionscript 3.0 and the GreenSock TweenLite to load images in through XML in flash. When you click the button (btn1) to go to the next image, it animates in perfectly, but since I am multiplying 140 each time, if I click btn1 while the image is transitioning in, it adds another 140 to that value and the next image goes off the screen. Think of it as a slot machine effect, witch is pretty much what it looks like. The images load in as if they're on a reel, vertically. I would like to know how to set a limit so that instead of adding 140 to the value, it goes to the next image instead, and centers it perfectly in the mask I have set up. Do you guys get what I am trying to do? If not, I can zip the folder up and attach it here, but it's a project for a client so I'm a bit weary.

Again, quick summary: btn1, if clicked more than once during the span of the image transitioning in (through XML and gs.tweenlite), the image gets 140 added to its positional value and goes off the screen.

Code:
import gs.TweenLite;
var id:int=0;
var list:XMLList;
var xmlLoader:URLLoader = new URLLoader();

[Code].....