var FormX,FormY;
 function SetPosition(){
   with(document.getElementById('DivId')){
     FormX=offsetLeft;
     FormY=offsetTop;
   }
 }
 function UpdatePosition(){
   with(document.getElementById('DivId')){
     style.left=(FormX+document.body.scrollLeft)+'px';
     style.top=(FormY+document.body.scrollTop)+'px';
   }
 }