Hello,

This could be possible with client-side events. It really depends on your scenario which client-side event to choose (are you using Row Template, or in place editing) - but you can pick some of the"BeforeXXX..." event described here:

http://help.infragistics.com/Help/NetAdvantage/NET/2008.2/CLR2.0/html/WebGrid_Client_Side_Events_CSOM.html

and cancel it (by returing true from the event handler) if the row being editied is not the last row (this information is typically available from the event handler arguments passed to the client-side event handler)

The client side row object is documented here:

http://help.infragistics.com/Help/NetAdvantage/NET/2008.2/CLR2.0/html/WebGrid_Row_Object_CSOM.html