var currentpos,timer; 

function initialize() 
{ 
timer=setInterval("scrollwindow()",50);
} 
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