Commonly asked question: Can Backup Exec backup data to an FTP server/Web server/Other online backup service?
This is not possible at all in versions previous to 12, however Symantec have recently launched the Symantec Protection Network, an online backup service. Currently this is only available in North America. Backup Exec 12 can use SPN as a backup device.
If you want to do an online backup of Backup Exec's own backup-to-disk backup you could replicate the .BKF files using something like DFS, Replication Exec, or anything similar.