Help on this script

stop();
import flash.filters.BlurFilter;
import flash.geom.Rectangle;
var speed:Number = 3.8;
var numButtons:Number = 6;
var blFilter:BlurFilter = new BlurFilter(0, 0, 1);
var imgDist:Number = 605;
var mask:Rectangle = new Rectangle(0, 0, 601.7, 399.9);
slider_mc.images_mc.scrollRect = mask;
function initButtons():Void {
	for (var i = 0; i<numButtons; i++) {
		var btn:MovieClip = this["b"+i];
		btn.targetx = (i*imgDist);
		btn.onRelease = function() {
			blurTo(slider_mc.images_mc, this.targetx);
		};
	}
}
function blurTo(mc:MovieClip, tx:Number):Void {
	mc.onEnterFrame = function() {
		var dx:Number = tx-mask.x;
		var blurAmount:Number = Math.abs(dx);
		blFilter.blurX = blurAmount;
		this.filters = [blFilter];
		var movex:Number = dx/speed;
		mask.x += movex;
		this.scrollRect = mask;
		if (Math.abs(tx-mask.x)<1) {
			delete this.onEnterFrame;
			this.filters = null;
			mask.x = tx;
			this.scrollRect = mask;
		}
	};
}
initButtons();

I´m using this script that i found in kirupa´s forum.
And what i want to now is, how can i detect the button that has been clicked. If someone could help me please.

Thank´s in advanced