var timerID = null;

  function getObj(objid) 
  {
    if (document.getElementById)
      return document.getElementById(objid)
    if (document.all)
      return document.all[objid]
    if (document.layers)
      return document.layers[objid]
    return null
  }
  
  function ScrollUp(elementName, step, speed) {
    var el = getObj(elementName);

    if (el != null) {
      if (isNaN(parseInt(el.style.top))) {
        el.style.top = "0px";
      }
      if (parseInt(el.style.top) < 0) {
        if ((parseInt(el.style.top) + speed) > 0) {
          el.style.top = "0px";
        }
        else {
          var changePlacement = parseInt(el.style.top) + speed;
		  el.style.top = changePlacement+"px";
        }
      }
      ScrollStop();
      timerID = setTimeout("ScrollUp('" + elementName + "', " + step + ", " + speed + ")", speed);
    }
  }

  function ScrollDown(elementName, step, speed) 
  {
    var el = getObj(elementName);
    if (el != null) 
	{
      if (isNaN(parseInt(el.style.top))) 
	  {
        el.style.top = "0px";
      }
      if (parseInt(el.style.top) > el.parentNode.offsetHeight - el.offsetHeight) 
	  {
        if ((parseInt(el.style.top) - speed) < el.parentNode.offsetHeight - el.offsetHeight) 
		{
          var changePlacement = el.parentNode.offsetHeight - el.offsetHeight;
		  el.style.top = changePlacement+"px";
        }
        else 
		{
          var changePlacement = parseInt(el.style.top) - speed;
		  el.style.top = changePlacement+"px";
        }
      }
      ScrollStop();
      timerID = setTimeout("ScrollDown('" + elementName + "', " + step + ", " + speed + ")", speed);
    }
  }

  function ScrollStop() {
    if (timerID != null) {
      clearTimeout(timerID);
      timerID = null;
    }
  }