From your description it sounds more like you need some kind of document storage / archival system than Backup Exec. Why do you only want to backup the data to tape after a month rather than backing it up more regularly?
Since disk based backups are wonderful for fast backups and restores but useless for disaster recovery, if you office burnt down, or you had a flood or what ever, the only data you'd have available for restore from tape would be a minimum of a month old, which for most businesses at least would be very bad indeed!