Object.extend(Event, {
	wheel:function (event){
		var delta = 0;
		if (!event) event = window.event;
		if (event.wheelDelta) {
		  delta = event.wheelDelta/120;
		  if (window.opera) delta = -delta;
		} else if (event.detail) { delta = -event.detail/3; } 
		return Math.round(delta); //Safari Round
	}
});