function mouseWheel(obj,upfun,downfun){
    if(obj.attachEvent){
        obj.attachEvent("onmousewheel",fun,false);//IE
    }else if(obj.addEventListener){
        obj.addEventListener("mousewheel",fun,false);//谷歌
        obj.addEventListener("DOMMouseScroll",fun,false);//火狐
    }
    function fun(e){
        var ev=e||window.event;
        var num=ev.detail||ev.wheelDelta;
        if(num==-3||num==120){
            upfun()
        }else if(num==3||num==-120){
            downfun();
        }
    }
}

滚轮事件函数