Code:
panel_window = new Ext.FormPanel({
    labelAlign: 'center',
    collapsible: false,
    animCollapse: false,  
    //width:870,
    width: 875,
    buttons:[{text: 'Search',handler: function(){
        adrpt_title_tab1 = get_ad_Response_title();
        my_panel.items.each(my_panel.remove, my_panel);
        my_panel.items.clear();
        my_panel.autoLoad.url = 'ad_response_call.php';
        load_msg.show();
        my_panel.autoLoad.params = 
        {
         task        : 'GRID_DISPLAY'
        };
        my_panel.doAutoLoad();
    }}]
});                                
my_panel = new Ext.Panel({
    labelAlign: 'center',
    id:'my_panel',
    scope: this ,
    width: 875, 
    autoScroll:true,
    frame:true,
    items:[{}],
    autoLoad: { url: 'ad_response_call.php', method:'POST',callback: function(){load_msg.hide()},
    params: {task: 'GRID_DISPLAY'}}
})
It will help You