Progress on interval -but error after first change

programming flash
1

hello all,

I have this function on the first frame of my timeline:


var c:Number = -1;
 function changeColor()
 {
	if(c<4){
		c++
	}else{
		c=0;
	}
		var final_color:Array = new Array();
		final_color[0] = 0x999999; //gray
		final_color[1] = 0xFF0000; //red
		final_color[2] = 0x0066CC; //blue
		final_color[3] = 0xFF66CC; //pink
		final_color[4] = 0x00CC66; //green
		final_color[5] = 0x999999; //gray
		
		var colorInfo:ColorTransform=menu_mc.company_txt.transform.colorTransform;
		var colorInfoEx:ColorTransform=menu_mc.exhibit_txt.transform.colorTransform;
		var colorInfoCn:ColorTransform=menu_mc.contact_txt.transform.colorTransform;
		if(currentFrame==2){
			var colorInfoAb:ColorTransform=about_mc.tf_txt.transform.colorTransform;
			var alphaOverAb:Tween=new Tween(about_mc.tf_txt,"alpha",Strong.easeInOut,0,1,5,true);
			alphaOverAb.addEventListener(TweenEvent.MOTION_CHANGE,tweenToFinalAb);
			
			function tweenToFinalAb(event:TweenEvent):void
			{
	
				colorInfoAb.color = Color.interpolateColor(final_color[c],final_color[c+1],event.position);
				about_mc.tf_txt.transform.colorTransform=colorInfoAb;
				
			}	
		}
		
		if(currentFrame==3){
			var colorInfoXb:ColorTransform=exhibits_mc.ex_txt.transform.colorTransform;
			var colorInfoNx:ColorTransform=exhibits_mc.next_txt.transform.colorTransform;
			var colorInfoPs:ColorTransform=exhibits_mc.pause_txt.transform.colorTransform;
			var colorInfoPr:ColorTransform=exhibits_mc.prev_txt.transform.colorTransform;
		
			
			
			var alphaOverEx:Tween=new Tween(exhibits_mc.ex_txt,"alpha",Strong.easeInOut,0,1,5,true);
			alphaOverEx.addEventListener(TweenEvent.MOTION_CHANGE,tweenToFinalEx);
			
			function tweenToFinalEx(event:TweenEvent):void
			{
	
				colorInfoXb.color = Color.interpolateColor(final_color[c],final_color[c+1],event.position);
				exhibits_mc.ex_txt.transform.colorTransform=colorInfoXb;
				colorInfoNx.color = Color.interpolateColor(final_color[c],final_color[c+1],event.position);
				exhibits_mc.next_txt.transform.colorTransform=colorInfo;
				colorInfoPs.color = Color.interpolateColor(final_color[c],final_color[c+1],event.position);
				exhibits_mc.pause_txt.transform.colorTransform=colorInfo;
				colorInfoPr.color = Color.interpolateColor(final_color[c],final_color[c+1],event.position);
				exhibits_mc.prev_txt.transform.colorTransform=colorInfo;
				
			}	
		}
		
		if(currentFrame==4){
			var colorInfoCt:ColorTransform=cnt_mc.ct_txt.transform.colorTransform;
			var alphaOverCt:Tween=new Tween(cnt_mc.ct_txt,"alpha",Strong.easeInOut,0,1,5,true);
			alphaOverCt.addEventListener(TweenEvent.MOTION_CHANGE,tweenToFinalCt);
			
			function tweenToFinalCt(event:TweenEvent):void
			{
	
				colorInfoCt.color = Color.interpolateColor(final_color[c],final_color[c+1],event.position);
				cnt_mc.ct_txt.transform.colorTransform=colorInfoCt;
				
			}	
		}
		
		var alphaOver:Tween=new Tween(menu_mc.company_txt,"alpha",Strong.easeInOut,0,1,5,true);
		alphaOver.addEventListener(TweenEvent.MOTION_CHANGE,tweenToFinal);
		
		function tweenToFinal(event:TweenEvent):void
		{
			colorInfo.color = Color.interpolateColor(final_color[c],final_color[c+1],event.position);
			menu_mc.company_txt.transform.colorTransform=colorInfo;
			colorInfoEx.color = Color.interpolateColor(final_color[c],final_color[c+1],event.position);
			menu_mc.exhibit_txt.transform.colorTransform=colorInfo;
			colorInfoCn.color = Color.interpolateColor(final_color[c],final_color[c+1],event.position);
			menu_mc.contact_txt.transform.colorTransform=colorInfo;
		
	
		}	
		
 }
setInterval(changeColor,6000);

you can see that I am using the conditional if(currentFrame==x) to apply to the mc’s not on frame1

This works fine except when I navigate off frame 1 and then between frames 2-4 - I get a
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at MethodInfo-62()
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at fl.transitions::Tween/setPosition()
at fl.transitions::Tween/update()
at fl.transitions::Tween/set time()
at fl.transitions::Tween/nextFrame()
at fl.transitions::Tween/onEnterFrame()
(actually I get quite a few of these)

what am I doing wrong??

Thanks