Would be grateful for clarification on which dates are needed.
As the two date fields are coming from different tables,
are you joining them together, or blending?
If you are joining, would it work for your join dialog
to directly connect [tblproduction] from the first file to [tbladjustments] from the second,
so the that resultant set will only have those rows where the two dates match?
If you need all the rows of tbladjustments even when there isn't a match,
you could try a calculated field of:
IF [tblproduction] = [tbladjustments] THEN [prodvalue]+[adjusmentvalue] // or whatever value you need
ELSE 0 END