Hi,
i am maintaing a excel tracker in shared drive where i am manually entering
the time when a person came into the office. Is it possible that when a
person comes he himself open the shared file and click the cell corresponding
to his name so that the time of that moment can be stored and that can not be
further updated with new value (time)...

below is the format
Name of Person
Date Name A Name B Name C
21-Apr-10 6:44 PM 6:48 PM 6:40 PM
22-Apr-10 6:30 PM 6:34 PM 6:31 PM
23-Apr-10 6:35 PM 6:39 PM 6:40 PM