Simulate Auto Number using Trigger

Iam trying to simulate Auto Numbers (MS Access type) in SQL Server 2000 using Triggers.. any help appreciated.
I know i can do that i n SQL Server using identity, but i have some logic to generate auto numbers, which i cant do using identity.
Thanks in Advance.
[280 byte] By [sihikahi] at [2007-11-18 18:13:42]