need for customer exit code to go to previous date

In the ODS there is a date which is a user entry on my report. I need to write a customer exit which goes to previous date.

In other words let's say user entered 07/07/07 at the user entry, and there is no activity for the entered date. The previous activity date in ODS data is 07/05/07. The report should run based on the previous date. ( Date is the key by the way )

I will appreciate any help with points,

Regards,

Mike