var scrollPosition = 0;
var scrollBox; //See body onload attribute for initialisation
var maxScroll = 0; //See body onload attribute for initialisation
var upBtn;  // See body onload
var downBtn;  // See body onload
var numImg; // See body onload
var imgSize = 74; //pixel height + margin/border underneath
var inc = imgSize * 5;

//Preload images
img = new Image(1,1); 
img.src="graphics/up.gif";

img1 = new Image(1,1); 
img1.src="graphics/down.gif";

function scrollDiv(direction) {

  if(direction == 'D') {
    if(scrollPosition < maxScroll) { // If not at bottom
      scrollPosition += inc;
    }
  }
  else {
    if(scrollPosition >= inc) { // If not at top
      scrollPosition -= inc;
    }
  }

  scrollBox.scrollTop = scrollPosition;

  //alert("scrollPosition: " + scrollPosition);

  if(scrollPosition >= maxScroll) { downBtn.src = "graphics/down_inactive.gif"; }
  else{ downBtn.src = "graphics/down.gif"; }

  if(scrollPosition <= 0) { upBtn.src = "graphics/up_inactive.gif"; }
  else{ upBtn.src = "graphics/up.gif"; }

}

function activateDownScroll() {
 
  if(document.getElementById('photoScroll').getElementsByTagName('img')[5]){
    downBtn.src = "graphics/down.gif";
  }
}

function setAsMain(obj){
  var regExp = /\/thumbs/;
  var tSrc = obj.src;
  
  document.getElementById('mainPic').src = tSrc.replace(regExp, "");
}