Hi Rekha,
Attached is the simple sample in which the Callback panel is placed inside the Webparts.
CallBackPanel_WebParts.zip* In our sample selecting the Listbox items will invokes the Callback refresh event and displays the seleted item in the Label box.
Let us know if you need any other assistance.
Thanks for using Syncfusion products.
Regards,
Gokulkumar.B