you could use on the Webclient an agent locking function:
Declarations
Dim Lock_ID as integer
...

Sub Intialize()
Lock_ID = CreateLock("number") 'generate Lock Object
call sequential_numbering() 'call sub
End Sub

Sub sequential_numbering() 'can only run if the Lock Object is free
Dim checklock as Variant 'to check status of Lock Object
checklock = CodeLock(Lock_ID) 'try to get a free Lock Object
While checklock = False 'if Lock Object is in use
Sleep(3) 'wait 3 seconds
checklock = CodeLock(Lock_ID) 'try it again so long until Lock Object is free
Wend
...
'now set the number if checklock is true
...
checklock = UnLockCode(number) 'free Lock Object, so parallel, same agents can run
End Sub

Sub Terminate()
Lock_ID = DestroyLock(Lock_ID) 'destroy Lock Object
End Sub


Or switch to R6, which embeds locking features finally.

Or you could use the function @Unique without a parameter!

the above mentioned locking method just applies to the web interface. The Notes client cant use one and the same process since the process is triggered on each client and not on the server, as the Domino server does handle HTTP requests (agent calls !!!) by users centrally.

The unique number is declared by the Notes help to be unique but i would consider a quick scan of the LDD boards to be sure.

Bogdan, beware, the locking mechanism only applies to the Web and NOT to the Notes Client. There is simply no process locking function in R5 !!! Your way by using a file is hereby the best and i wouldnt change it, since you can use it for the Web too, or was there a special reason you deny this solution here?

Read this please: http://www-10.lotus.com/ldd/today.nsf/62f62847467a8f78052568a80055b380/74bd0cdadb2602c385256b56001c0517?OpenDocument&Highlight=0,unique#Preparing%20an%20application%20for%20sequ


and Julie from IRIS:
Lets listen to Julie Kadashevich from IRIS:
Lock functions are currently supported for web agents
(unrelated to any hardware configurations), they are
not supported in Notes server-based agents (such as
scheduled agents).

The reason for that that the locks are effective within
the same PROCESS (such as a web server). And if one understands
the architecture of the scheduled agents, they are not always
within the same PROCESS. So it is unrelated to the mutilple processors
on the server.

By the way, this is probably obvious, but just stating it for
completeness, if you happen to use the same lock in two applications
than do not run in the same process - then nothing will happen (i.e.
no lock, no hang, no data protection). It is a NOOP.

Julie - iris

the writing right should be applied to a runon server agent and not a user triggered agent. So the server has the right to write. Could this be a way?

The problems are mentioned hereby already.

So you can try to use @unique in both worlds: Notes and Web.

@unique is not a sequential number, its a random number, see the help please  

So the user needs the number immidiately? Where is there a problem with a runonserver agent? You can run the agent, wait until its finished and get the number visually back for the user.
See below the bold line:
"If agent.RunOnServer(doc.NoteID) = 0 Then"
Thats the user trigger mechanism. If the numbering process is finished you can reload your doc and get hereby the number for the user.

See the help:
This agent runs the agent named "Agent to be run parameter LotusScript," passing it the note ID of a newly created document.
Sub Initialize
  Dim s As New NotesSession
  Dim db As NotesDatabase
  Dim doc As NotesDocument
  Dim agent As NotesAgent
  Set db = s.CurrentDatabase
  REM Create document containing data to be passed
  Set doc = New NotesDocument(db)
  doc.TriggerUserName = s.UserName
  Call doc.Save(True, False)
  REM Start agent and pass note ID of document
  Set agent = _
  db.GetAgent("Agent to be run parameter LotusScript")
  If agent.RunOnServer(doc.NoteID) = 0 Then
    Messagebox "Agent ran",, "Success"
  Else
    Messagebox "Agent did not run",, "Failure"
  End If
End Sub
This is "Agent to be run parameter LotusScript." It accesses the passed note ID through ParameterDocID, accesses the referenced document, and removes it.
Sub Initialize
  Dim s As New NotesSession
  Dim agent As NotesAgent
  Set agent = s.CurrentAgent
  Dim db As NotesDatabase
  Dim doc As NotesDocument
  Set db = s.CurrentDatabase
  REM Get document used for passing data
  Set doc = db.GetDocumentByID(agent.ParameterDocID)
  REM Send mail containing passed data
  Dim memo As New NotesDocument(db)
  memo.Form = "Memo"
  memo.SendTo = s.UserName
  memo.Subject = "Message from LotusScript agent"
  memo.Body = "The agent was started by " _
  & doc.TriggerUserName(0)
  Call memo.Send(False)
  REM Delete document used for passing data
  Call doc.Remove(True)
End Sub

Hey, Bogdan, you dont like the Help DB, eh?  

something new ?