function moveElement(elementID,final_x,final_y,interval) {
  if (!document.getElementById) return false;
  if (!document.getElementById(elementID)) return false;
  var elem = document.getElementById(elementID);  
  var ypos = parseInt(elem.style.marginTop);
  if (ypos <= final_y) {
    ypos+=1;
  }
  if (ypos >= final_y) {
    ypos-=1;
  }
  elem.style.marginTop = ypos + "px";
  var repeat = "moveElement('"+elementID+"',"+final_x+","+final_y+","+interval+")";
  movement = setTimeout(repeat,interval);
}