using modulus to loop thumbnails

[tonyxspote]

I'm still pretty novice when it comes to as3 and am trying to use modulus to loop 14 thumbnails in an array.

i have a property called firstThumb that keeps track of the first thumbnail being displayed and a forward and back function that looks like this

private function reverseThumbs(e:MouseEvent):void
        {
            trace("moving back");
            displayThumbs(firstThumb-1, DISPLAYED);
            
            //update our pointer to the first thumb to display
            
            
            firstThumb--;
            
    } 

private function advanceThumbs(e:MouseEvent):void
        {
            trace("moving forward");
            displayThumbs(firstThumb+1, DISPLAYED);;
            
            //update our pointer to the first thumb to display
            
            
            firstThumb++;
            
            
        } 

i also have a position counter to keep track of the thumbnails being displayed

//display some of the thumbs in the thumbarray
        private function displayThumbs (aStart,howMany:int):void
        {
            
            //13%14 modulus 
            //get rid any thumbs already displayed
            for (var n = firstThumb; n < firstThumb+DISPLAYED; n++) 
            {
                
                
                //remove the thumb if it is in the displaylist
                if (this.contains(thumbArray[n])) removeChild(thumbArray[n]);
                
            }
            
            //then display the current four
            var posCounter:int =0;
            for (var i = aStart; i < aStart+howMany; i++)
            
            {
                addChild( thumbArray[i] );
                thumbArray[i].y = 45;
                thumbArray[i].x = 150 +posCounter*(thumbArray[i].width + MARGIN);
                posCounter++;
            }
            
        } 

if anyone has any suggestions for how i can go about using modulus to loop the images through, itd be great