var timerId;
var scrollUnit = 10;
var objectScrollUnit = 10;
var objectToScroll;
var containerObject;

function stopScrolling() {
	window.clearInterval(timerId);
}
function startObjectScrolling(object, container, functionName) {
	objectToScroll = object;
    containerObject = container;
	timerId = window.setInterval(functionName, 50);
}
function scrollObjectUpwards() {
	if (parseInt(objectToScroll.style.top) < 0)
		objectToScroll.style.top = String(parseInt(objectToScroll.style.top) + scrollUnit) + "px";
	else
		stopScrolling();
}
function scrollObjectDownwards() {
	if (parseInt(objectToScroll.style.top) > (containerObject.offsetHeight - objectToScroll.offsetHeight))
		objectToScroll.style.top = String(parseInt(objectToScroll.style.top) - scrollUnit) + "px";
	else
		stopScrolling();
}
function scrollUpwards(object, containerObject) {
	startObjectScrolling(object, containerObject, "scrollObjectUpwards()")
}
function scrollDownwards(object, containerObject) {
	startObjectScrolling(object, containerObject, "scrollObjectDownwards()")
}