var scrollInterval;
var scrollSpeed = 50;
var scrollHeight = 5;
var UpButtonId="butUpAfstemninger";
var DownButtonId="butDownAfstemninger";
var UpDisabledClass="butUpDisabled";
var DownDisabledClass="butDownDisabled";
var UpClass="butUp";
var DownClass="butDown";

function scrollStart(direction, divID)
{   
    eval("scroll"+direction+"('"+divID+"')");
    scrollInterval = setInterval("scroll"+direction+"('"+divID+"')", scrollSpeed);
}

function scrollEnd(which)
{
    clearInterval(scrollInterval);
}

function scrollUp(which)
{
    var el = document.getElementById(which);
    if (el)
    {        
        var val = el.scrollTop - scrollHeight;
        el.scrollTop =  (val <= 0 )? 0 : val; 
        if (el.scrollTop == 0)
        {
            scrollEnd(which);
            
            var but = document.getElementById(UpButtonId);
            if (but)
            {
                but.className = UpDisabledClass;
            }
        }
        
        var butD = document.getElementById(DownButtonId);
        if (butD)
        {
            if(butD.className == DownDisabledClass)
            {
                butD.className = DownClass;
            }
        }
    }
}
function scrollDown(which)
{
    var el = document.getElementById(which);
    if (el)
    {        
        var val = el.scrollTop + scrollHeight;
        el.scrollTop = val;
        if (el.scrollTop !=  val)
        {
            scrollEnd(which);  
            
            var but = document.getElementById(DownButtonId);
            if (but)
            {
                but.className = DownDisabledClass;
            }   
        }
        
        var butU = document.getElementById(UpButtonId);
        if (butU)
        {
            if(butU.className == UpDisabledClass)
            {
                butU.className = UpClass;
            }
        }
        
    }
}