OK, I'll try.
Not knowing what your table structure is like, I imagine you have a DATE field in there.
if you use the following syntax in your select statement, for example..
SELECT *, week(DATE) as week FROM tablename, (where DATE is the name of your date field)
You will have a column called week returned, with a value of between 1 and 52.
if you can't get to grips with this, drop me a PM or post a reply.