function scroll(){
    var tmt;
    var cntnt = document.getElementById('Scroll');
    var arr   = document.getElementById('arrow_up');
    if( !cntnt && !arr ) return;
    var arrow = arr.src.substr(arr.src.length-5,1);
    var set_a = (arrow == 'A' ? 'A' : 'C');
    var set_b = (arrow == 'A' ? 'B' : 'D');
    var upp   = arr.parentNode;
    upp.onmouseover = function(){
	upp.firstChild.src="images/b_arrow_up-"+set_b+".gif";
	tmt = window.setInterval('customScrollBy(-5)',50);
    };
    upp.onmouseout = function(){
	upp.firstChild.src="images/b_arrow_up-"+set_a+".gif";
	window.clearInterval(tmt);
    };
    downn = document.getElementById('arrow_dn').parentNode;
    downn.onmouseover = function(){
	downn.firstChild.src="images/b_arrow_dn-"+set_b+".gif";
	tmt = window.setInterval('customScrollBy(5)',50);
    };
    downn.onmouseout = function(){
	downn.firstChild.src="images/b_arrow_dn-"+set_a+".gif";
	window.clearInterval(tmt);
    };
}
function customScrollBy(amnt){
    var cntnt = document.getElementById('Scroll');
    cntnt.scrollTop += amnt;
}

addEvent(window, 'load', scroll);