var currentpos,timer; 
function initialize() 
  {timer=setInterval("scrollwindow()",1);} 
function sc()
  {clearInterval(timer); }
function scrollwindow() 
  { currentpos=document.body.scrollTop;
    window.scroll(0,++currentpos);
    if (currentpos != document.body.scrollTop) 
         {sc();}
  } 
document.onmousedown=sc
document.ondblclick=initialize