Is the dropdown getting this data from a table?

I suggest to populate a table with the following structure

TableName: Weeks
Field :
Week_ID
Week_Number
Week_EndDate

The source for the Combobox should be set to : Week_Select for which the SQL :
SELECT Week_ID, Week_Number, Week_EndDate FROM Weeks ORDER BY Week_Number DESC

Then on Form_Open you should perform the following code :

cmbWeeks=DLookup("Week_ID","Week_Select","Week_EndDate<=Date()")

I think this will do the trick.

- Raoul