How to format a personal vault before via pre-backup command?

Hi,

I need to format the target personal vault (a USB drive) before the backup commences. for now, I've scheduled this separately with Windows task scheduler, but prefer to do so via pre-command. Problem is that doing so sees the .meta dir cleared literally after the backup job has started, so at the end of the backup, Acronis complains that it can't access the backup (associated with the TIB file) data properly (though the TIB appears to be fine).

If i format the drive immediately before running the backup job, this problem does not occur.

Even if I could see a "keep max N backups in the vault" option, I couldn't rely on that since other backup systems also send data to that USB drive.

Also note that I'm using the Custom backup scheme with a daily schedule set - just a full system backup every night.

How is one meant to do this? Ideally, I'd like for the backup job to have an option" erase vault before backup", but I can't see that option. It appears that one of the other common Acronis backup tools does have this option, though.

I'm running B&R 10 AS - SBS Edition V 10.0.12457 on SBS 2003.