Give a sign when data has changed in GridView

If u want to do something as the result of Partial Postback(in here the change of data in gridview) in a UpdatePanel,I think you could use a trigger.

Trigger's trigger the update panel to do something based on another event, they have nothing to do with monitoring the status of the updatepanel itself.

What you want to do is call Sys.WebForms.PageRequestManager.getInstance().add_endRequest(someFunction) where someFunction is custom code in javascript you want fired when the UpdatePanel is done. Conceivably, you could inspect the EndRequestEventArgs object that gets passed to someFunction as its first parameter to glean information about the request. You might have to maintain some kind of state on the client to pull this off.