var UpdateInterval = 1;
var PixelPerInterval = 5;
var scorllerInterval;

function start_scroll_up()
{
	scorllerInterval = setInterval(scroll_up, UpdateInterval);
}

function scroll_up()
{
	document.getElementById('scroller').scrollTop -= PixelPerInterval;
} 

function start_scroll_down()
{
	scorllerInterval = setInterval(scroll_down, UpdateInterval);
}

function scroll_down()
{
	document.getElementById('scroller').scrollTop += PixelPerInterval;
}

function stop_scrolling()
{
	clearInterval(scorllerInterval);
}