how to update records using modelpopup

Did you mean modal, not model? If so, then I am sorry; I know what modal dialogs and forms are but they are windows, not databases, so I know nothing about that. It sounds very strange to me.

Sample how to use ajax modal pop up extender
http://www.asp.net/ajax/ajaxcontroltoolkit/Samples/ModalPopup/ModalPopup.aspx