Need help on auto pop through a form

[David]

Hi, I am trying to have a 'time out' field auto populate when the user
comes into the record the second time. The first time when the user
creates the record, the 'time in' field is auto populated by the code:
Format(Time(),"Medium Time") in the table's default value. The user
opens the record the second time through a form. I have tried to use
the above code in the empty 'time out' textbox's default value, but
nothing happens. I have also tried 'if' statements in the 'on open
Event Procedure', but have not been successful yet. Can anyone help
me? Thanks much. David