Date field

[Ana]

I have a form to input information on appointments for the week. The form tracks information based on field week_ending. For example, for week ending 11/14/03, appointments for reps x, y and z where scheduled. How can I set up the form so that whenever I select a new record, the previous week ending value (i.e., 11/14/03) is remembered, so that I will only change it when there's a new week ending to track

Thanks

Ana