Backup VM greetings, but not VM's

Hello all,
so, when backing up the VM folders under backup/resotre, ( freePbx 2.9),the entire mailboxes get backup, in a way that if the restore will be done in 3 months, the user will have "new messages ", but 3 months old.
is it possible to run the backup schedule without backing up the messages, but still backup up the VM greetings ?

Thank you .