You probably need to buy a Domino API from Veritas and use that option for backups. When the Domino API is called by the backup exec, it communicates with Domino to negotiate a lock on the file. Any changes that need to occur to that file are stored in a .BIB file until Veritas is done backing it up. When the Veritas Domino API releases the lock, Domino writes changes stored in the .BIB to the file.
You backup is then a file that can be restored and there are no conflicts with Domino.
I learned about this last week, so this is the sum total of everything I know on the subject.