向下滚动某个div后,JQuery浮动div停止

http://jsfiddle.net/sasindu555/xaYTt/

我想在向下滚动停止div后停止浮动special_features div.怎么做请帮我.谢谢.

var name = "#special_features";  
    var menuYloc = null;  

    $(document).ready(function(){  
        $(name).css("top", $("#start").offset().top - 10);
        menuYloc = parseInt($(name).css("top").substring(0,$(name).css("top").indexOf("px")))  
        $(window).scroll(function () {  
            var offset = menuYloc+$(document).scrollTop();  
            if(offset > $("#stop").offset().top){
                offset = $("#stop").offset().top - 10; 
            }
            else if(offset < $("#start").offset().top){
                offset = $("#start").offset().top - 10; 
            }
 offset = offset+"px";           $(name).animate({top:offset},{duration:500,queue:false});  
        });  
    });