var imgs = new Array(); 
var imgcnt = 0; 
var thisimg = 0;


function addImg(url)
{
  imgs[imgcnt++] = url;
}

function nextImg() {
if (document.images) {
  thisimg++;
  if (thisimg >= imgcnt) thisimg = 0;
  document.slideshow.src = imgs[thisimg];
}
}
function prevImg() {
if (document.images) {
  thisimg--;
  if (thisimg < 0) thisimg = imgcnt-1;
  document.slideshow.src = imgs[thisimg];
}
}