I am supposing you wish to implement sequential document numbers.
You need to be very careful on doing this. First thing is : Notes is not capable of doing sequential numbering for multiple authors. It is against the philosphy of a distributed environment. The issue is, since a Notes db can be replicated, there is no guarantee that two users in seperate replicas will avoid creating a doc with the same number.
If you can avoid replicating the db, then you can try a number doc in a special view, with semaphore-type access and hope it will hold out. If it works, it will only work until the day someone replicates the db to another server, or locally.
The best, safest way to do sequential numbering in Notes is per user. Each user can have a profile doc with his number, and that will be incremented normally. Of course, this supposes that only one user is using the ID at the time.
As you can see, putting a sequential number on a document is not an easy task.
Does this answer your question ?