function aroll(richtung)
{

if (richtung == 'up')
	{
	rooster_iframe.scrollBy(0, -20);
	rollen = window.setTimeout("aroll('up')", 10); 
	}

if (richtung == 'down')
	{
	rooster_iframe.scrollBy(0, +20);
	rollen = window.setTimeout("aroll('down')", 10); 
	}
    }

function stoppit () {
  	window.clearTimeout(rollen);
    }