Capturing actions: Scroll Down and Scroll Up

Is there any way in jQuery to capture the events of "ScrollDown" and "ScrollUp"?

I tried this way:

var lastScrollTop = 0;
$(window).scroll(function(event){
   var st = $(this).scrollTop();
   if (st > lastScrollTop){
      // downscroll code
   } else {
      // upscroll code
   }
   lastScrollTop = st;
}); 

But it does not capture the UP and DOWN functions, but the scroll function!

And I wanted that as soon as the mouse roll was fired the function would be executed.

Is this possible?