I had a problem similar to this, but ended up not going for it, however, one thought i had was:
add an extra field to the tables you are querying, this can be text. In this field when you insert data, you would insert an id that would represent the week.
say, for week 1 2006 you could use
01-2006 or even 012006
then in your qeuries, your normal queries would work ok, but the page where you wish to save the "weekly" data - you would have the SQL as before but iwth the clause WHERE WEEK_ID="01-2006"
not the most elegant - but it's starter, and it would work.
S