var cjValue = Ext.getCmp("combo_qjzc").value;
var cbg_obj=Ext.getCmp('cbg_id');
var items=cbg_obj.items,
columns=cbg_obj.panel.items,
column=columns.itemAt(items.getCount()%columns.getCount()),
checkbox=column.add({boxLabel:'guoguo',name:'1'});
items.add(checkbox);
items.items.remove('1',true);
cbg_obj.doLayout();