Im using a script to detect scroll up to click a previous link. I want to detect scroll up even when your top of the page and do a scroll up. Now I have to scroll down a bit then up again. How can I do this?

Code:

 var lastScrollTop = 0, delta = 5;
     jQuery(window).scroll(function(){
         var nowScrollTop = jQuery(this).scrollTop();
         if(Math.abs(lastScrollTop - nowScrollTop) >= delta){
            if (nowScrollTop > lastScrollTop){
                // ACTION ON
                // SCROLLING DOWN 
            } else {
            jQuery( 'a.action.previous' ).click ();

            }
         lastScrollTop = nowScrollTop;
         }
     });