I'm working in flash Cs4 and I just learned cash and I'm wondering if there's a way to use the Uiloader to load multiple images and have them change every couple of secondes like msn or actionvillage. This is my code so far:

next_btn.addEventListener(MouseEvent.CLICK, nextImage);

var imageNumber:Number = 1

function checkNumber():void
{
next_btn.visible=true;
back_btn.visible=true;

if(imageNumber>3){
trace(imageNumber);
//next_btn.visible = false;
imageNumber = 1;
}
}
function checkNum():void
{
if(imageNumber<1){
imageNumber = 3;
}
}


function nextImage (evtObj:MouseEvent):void
{
imageNumber++;
checkNumber();
largeImageLoader.source = "images/poster"+imageNumber+".png";
}

back_btn.addEventListener(MouseEvent.CLICK, backImage);

function backImage (evtObj:MouseEvent):void
{
imageNumber--;
checkNum();
largeImageLoader.source = "images/poster"+imageNumber+".png";

}
I have buttons below my uiloader that changes the images when you click on the manually but when you don't click on the arrows I would like the images to change automatically.

Any help would be appreciated, thank you.