Thanks for your suggestion. I started implementing this but I don't think it will work in my situation. I want every Part to look at ALL Test records to get the average "Efficiency" for all Tests which have FirstDayOfWeek([Test Date]) = FirstDayOfWeek([Part Ref Date]).
So if I have the relationship one Part < many Tests, your process only works for the Part to summarize its related Tests, and not all of them. Perhaps I need some intermediate step to facilitate a many-to-many relationship and build up the summary fields, but I can't figure out how to do it.
To break the problem down to an earlier stage, what I really need is to automatically create a weekly summary field or record that summarizes the average Efficiency of all Tests from the previous week. Then I can hopefully relate this table of weekly summaries to my Parts table and pull the reference average Efficiency related to the week from which the Part was built. I'm not sure how to go about these steps though, or if they're possible with native QB capability.
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Graeme
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