addEventListener not detected


I have a problem that is driving me nuts. Essentially I am loading a swf dynamically into a class. (SlideControlsMC) I can access the movieclips within the swf, and change things like alpha, x etc. But when I come to put an eventlistener on an MC, it simply isn’t detecting it.

I checked the depth of the SlideControlsMC and it is above everything else. I have imported the requred and when I compile, I get no errors.
The following is the code I am using add the eventlistener.

_slider.buttonLeft.buttonMode = true;
_slider.buttonLeft.useHandCursor = true;
_slider.buttonLeft.addEventListener(MouseEvent.CLICK, functionName)

This is how I am bringing in the .swf

private function loadSlider():void {
			_sliderLoader = new Loader();
			_sliderLoader.load(new URLRequest("interface/slidecontrols.swf"));
			_sliderLoader.x = 0;
			_sliderLoader.y = 0;			

		public function addSlider(e:Event):void {
			_slider = new SlideControlsMC;
			// position slider
			// hide all of the markers
			for (var i=0; i<=9; i++) {
				item_mc = MovieClip(_slider.getChildByName("s"+i));

Can anyone shed light on why I am not getting any response what so ever?

Thanks for your help.