Restrict cPanel backup visibility by date

We keep some backup sets for a long time. Our policy has always been to restore accounts at no charge if they were recent, but to charge a restore fee for bringing back older sets, to account for increased storage costs.

We would like to limit the number of backups a cPanel user can see to those less than X days old, preferably with a message along the lines of "There are older backups available, please contact your host for assistance." if there are more backups. This would allow us to continue charging for the service.