var old_position = 0;
var delta = 0;
var cumulative_delta = 0;

function scrollPosition2()
{
// get the scroll position
  var scrollbox = document.getElementById("scrollbox");
  var position = scrollbox.scrollLeft;
  var pars = 'position=' + position + '&old_position=' + old_position;
  delta = position - old_position;
  cumulative_delta += delta;
alert("in scrollPosision" + cumulative_delta);
}

function scrollPosition()
{
// get the scroll position
  var scrollbox = document.getElementById("scrollbox");
  var position = scrollbox.scrollLeft;
  var pars = 'position=' + position + '&old_position=' + old_position;
  delta = position - old_position;
  cumulative_delta += delta;
//alert("in scrollPosision, cumulative_delta = " + cumulative_delta);
  if (cumulative_delta > 25) {
    cumulative_delta = 0;
    new Ajax.Updater('thumbs', '/display/update_scrollbox', {parameters: pars});
  }
  old_position += delta;
}