Edit the main WADAUsers recordset for the page to use a join query to get the related data from the Discounts table:
SELECT Users.*, Discounts.disc_code
INNER JOIN Discounts
ON Users.User_DiscCode = Discounts.disc_code
This code will go in place of the SELECT ... FROM portion of the recordset, if there is a where clause, or order by clause, leave that in place untouched
this way the related disc_code will be returned for each record.