var currentpos,timer; 

function initialize() { 
   timer=setInterval("scrollwindow()",8);
} 

function sc(){
   clearInterval(timer);	
}
function scrollwindow() { 
   currentpos=document.body.scrollTop; 
   window.scroll(0,++currentpos); 
   if (currentpos != document.body.scrollTop) 
	  sc();
} 

document.body.onmousedown=sc
document.ondblclick=initialize