so i've got the scrolling background thing down for a side-scroller im making, but eventually i want to have the background image change from a wall to an outside scene, by changing the artwork as you walk along. i tried this but it's not working:

Code:
if (Key.isDown(Key.RIGHT)) {
			if (crouching == false) {
				wall._x -= 10;
				walking = true;
				player_mc.gotoAndStop("walk");
				if (wall._x<=800) {
					walliteration++;
					if (walliteration == 2) {
						wall.gotoAndStop("transition");
						transition = true;
					}
					if (transition == true) {
						wall.gotoAndStop("wall2");
						walliteration -= 50;
					}
					wall._x = 1600;
				}
			}
walliteration is supposed to change to different frames of the background after the wall scrolls past you a few times, but it's not changing.