jquery.fn.setscroll = function(_scroll,_scroll_up,_scroll_down,_scroll_bar){
    this.each(function(){
        
        var _bar_margin = 3;
        
        //create scroll dom
        var _scroll_control = jquery('<div class="scroll_zone">').width(_scroll.width).css({'position':'absolute','float':'none',margin:0,padding:0}).css('background','url('+_scroll.img+')');
        var _scroll_control_up = jquery('<img class="scroll_down">').attr('src',_scroll_up.img).width(_scroll.width).css({'z-index':'1000','position':'absolute', 'top':'0','float':'none',margin:0,padding:0});
        var _scroll_control_down = jquery('<img class="scroll_down">').attr('src',_scroll_down.img).width(_scroll.width).css({'z-index':'1000','position':'absolute', 'bottom':'0','float':'none',margin:0,padding:0});
        var _scroll_control_bar =  jquery('<img class="scroll_bar">').attr('src',_scroll_bar.img).width(_scroll.width).css({'z-index':'1500','position':'absolute','float':'none',margin:0,padding:0,height:_scroll_bar.height+'px'}).css('top',_scroll_up.height+_bar_margin+'px');
        
        _scroll_control.append(_scroll_control_up);
        _scroll_control.append(_scroll_control_bar);
        _scroll_control.append(_scroll_control_down);
        
        var _oheight = jquery(this).css('height').substring(0,jquery(this).css('height').indexof('px'));
        var _owidth = jquery(this).width();
        var _ocontent = jquery(this).html();
        
        if(jquery(this).attr('scrollheight')<=_oheight) return;
        
        var _content_zone = jquery('<div>').html(_ocontent).css({ width:_owidth-10+'px',height:_oheight+'px',overflow:'hidden','float':'none',margin:0,padding:0});
        
        jquery(this).css({'overflow':'hidden'});
        jquery(this).empty().append(_content_zone).css({position:'relative'}).append(_scroll_control.css({left:_owidth-_scroll.width+'px',top:'0',height:_oheight+'px',margin:0,padding:0}));

        //register drag event
        jquery(this).find('.scroll_bar')
        .mousedown(
            function(){
                jquery(document).mousemove(
                    function(e){
                      var _content = _content_zone.get(0);
                      var lastprogress = _scroll_control_bar.attr('progress');
                      _scroll_control_bar.attr('progress',e.pagey);
                      var nowprogress = _scroll_control_bar.css('top');
                      nowprogress = nowprogress.substring(0,nowprogress.indexof('px'));
                      nowprogress = number(nowprogress) + number(e.pagey-lastprogress);
                      var preprogress = nowprogress/(_oheight-_scroll_up.height-_scroll_down.height-_scroll_bar.height-(2*_bar_margin));
                      _content.scrolltop = ((_content.scrollheight - _content.offsetheight) * preprogress);
                      if(nowprogress<(_scroll_up.height+_bar_margin) || nowprogress > (_oheight-(_scroll_down.height+_scroll_bar.height+_bar_margin))) return false;
                      try{_scroll_control_bar.css('top',nowprogress+'px');}catch(e){}
                      return false;
                    }
                );
                return false;
            }
        )
        .mouseout(
            function(){
                jquery(document).mouseup(
                    function(){
                        jquery(document).unbind('mousemove');
                     }
                )
            }
        )
        
    }); 
}