var p = new Ext.Panel({
     title: 'My Panel',
     collapsible:true,
     width:400,
     id:’panel1’,
     html:'<iframe scrolling="auto" frameborder="0" width="100%" height="100%" src="PagingGrid.jsp"></iframe>'
     });

方法：

Ext.getCmp(‘panel1’).body.update( '<iframe scrolling="auto" frameborder="0" width="100%" height="100%" src="PagingGrid11.jsp "></iframe>');