Detecting direction of scroll

[gausie]

<script type="text/javascript">

function scrollPosition(){
	if (navigator.appName == "Microsoft Internet Explorer"){
		return document.body.scrollTop;
	}else{
		return window.pageYOffset;
	}
}

function dirScrolling(prev) {

	var current = scrollPosition();

	if (prev > current){
		document.getElementById('c').innerHTML = "V";
	}else if (prev < current){
		document.getElementById('c').innerHTML = "^";
	}else{
		document.getElementById('c').innerHTML = "=";
	}

	t = setTimeout(dirScrolling(current),500);

}

</script>

 

Why does this not change the div when I scroll?