var scrollamount = 2;	// pixel pro Scrollschritt
var scrolltimeout = 20;	// ms pro Scrollschritt

var scrollstep;
var scrolling = 0;
var scrolldoc;
var scrollmarkertop = 0;
var scrollTO;

function initScroll(scrollObj) {  // init
	scrolldoc = document.getElementById(scrollObj+'Doc');
	if(scrolldoc.offsetHeight < scrolldoc.parentNode.offsetHeight) {
		document.getElementById('scrollUp').style.display = 'none';
		document.getElementById('scrollDown').style.display = 'none';
		return;
	}
	else {
		document.getElementById('scrollUp').style.display = 'block';
		document.getElementById('scrollDown').style.display = 'block';
	}
	scrolldoc.style.top = 0;
	document.onmouseout = scrollstop;
}

function scroll() { // scrollen
	if(scrollstep > 0 && scrollstep + scrolldoc.offsetTop >= 0) { //ganz oben
		scrolldoc.style.top = 0;
		scrollstop();
	}
	else if(scrollstep < 0 && scrolldoc.parentNode.offsetHeight - scrolldoc.offsetTop - scrollstep >= scrolldoc.offsetHeight) { //ganz unten
		scrolldoc.style.top = scrolldoc.parentNode.offsetHeight - scrolldoc.offsetHeight;
		scrollstop();
	}
	else scrolldoc.style.top = scrolldoc.offsetTop + scrollstep;
	if(scrolling) scrollTO = setTimeout('scroll()',scrolltimeout)	
}

function scrollstart(down, scrollObj) {  // scrollen starten
	//scrolldoc = document.getElementById(scrollObj+'Doc');
	scrolling = 1;
	if(down) {
		scrollstep = -scrollamount;
	}
	else {
		scrollstep = scrollamount;
	}
	scroll();
}

function scrollstop() { // scrollen beenden
	scrolling = 0;
	if(scrollTO) clearTimeout(scrollTO);
}

function mousewheelscroll(scrollObj) {  // mousewheel für IE
	scrolldoc = document.getElementById(scrollObj+'Doc');
	if(scrolldoc.offsetHeight < scrolldoc.parentNode.offsetHeight) {
		scrolldoc.style.top = 0;
		scrolling = 0;
		return;
	}	
	scrolling = 1;
	if (event.wheelDelta >= 120) scrollstep = 10;	
	else if (event.wheelDelta <= -120)  scrollstep = -10;
	scroll();
	scrolling = 0;
}