How To Fine A Hole In A Records?

Hi all!

I need your help to realize algorithm for stored proc or trigger.

tool: MS SQL server 2000, T-SQL

TABLE:
[unique_id] [mynumber] [week]

[unique_id] - bigint,primary key, identity auto-increnment
[week] - int, 1-53, week number
[mynumber] - int, 1 - 7, for every week, daily record one per day, up
to 7 per week

so, for every week we have a mynumber from 1 to 7
or nothing (if no records for that day),

we can insert or delete mynubers in any order, at will

EXAMPLE:

week 1, mynumber 1,2,3 - so if we insert a new record, mynumber value
= 4
week 2, mynumber 1,2,3,5,7 - so next mynumber = 4

QUESTION:

How to use _only_ T-SQL find a missed numbers for particular week when
I'm insert a records?


Thanks.
Chapai