Maintaining Unix mailbox files

Hey everyone,

Does anyone know if I can use procmail/formail to remove old mail from users 
mailbox on a Linux machine?

What I want to have (eventually) is a cron-ran script that each day checks all 
the mailboxes (around a 100) and removes any mail older than a week. 
The idea behind this, is that this server works as a backup -
so it's only used if the main server dies.
For the record, I am using sendmail 8.11.2 and ipop3d on a RH 7.1 linux .

Thanks in advance,
Eugene