ExtJs 控制复选框disabled

var csm2 = new Ext.grid.CheckboxSelectionModel({
  //如果group为1的 为组角色选中，不让修改 
                            renderer:function(v,c,r){ 
                                    if(r.get("disabled")){ 
                                        return "<div class=\"x-grid3-hd-checker\">&#160;</div>"; 
//将复选框变 disabled的style
                                    }else{ 
                                        return  "<div class=\" x-grid3-row-checker\">&#160;</div> ";
//将复选框变 正常的 styele
                                    } 
                            },
                            header:'',singleSelect:true
//允许 单选，不能多选 默认为false
                            //不允许使用点击表格形式修改选择 
                           // handleMouseDown:Ext.emptyFn 
});