GridPanel TopBar Dynamic add button
gc.down('toolbar').add({xtype:'button',text:'NewButton',iconCls:'icon-tableadd',itemId:'btndn',handler:function(){debugger;}});
gc.down('toolbar').remove('btndn');
gc.down('toolbar').add({xtype:'button',text:'NewButton',iconCls:'icon-tableadd',itemId:'btndn',handler:function(){debugger;}});
gc.down('toolbar').remove('btndn');