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 
  } 
});