>
>SQL Server performs table, page, and row-level locking automatically:
>
>

>
>declare @Next int
>
>begin transaction
>    select @Next = invoice + 1 from DocsNumbers
>    update DocsNumbers
>        set invoice = @Next
>end transaction
>

>
>For more info about SQL locking, see "SET TRANSACTION ISOLATION LEVEL" in the BOL.

You don't need a transaction because it can be done in one UPDATE sytement. See Record ID generator question Message #611104