As others have suggested, we really need a copy of the database (ideally). The one with the macros converted to vba.
Can you look at the relationships window and see if tables are represented? If so take a screen shot and post.
Also, showing each of the table designs would be helpful, as Mark said.
You are "experimenting" with a copy of the database, correct?
People here are not concerned with the "business info/trade secrets" type of thing. We're trying to sort through the logic to ensure that whatever processes/programming is involved, it is working/calculating/reporting values according to specification.
A further thought/concern is that if this is an operational database and nobody knows the details; there is no available IT person/people with knowledge of the database and application; little to no documentation, then this org is in a quite vulnerable situation.
It's difficult to say where this application fits with the org, but someone(s) within the org should consider the importance of this database/info to the viability of their business and make some fundamental decisions. I'm a little concerned that a company with this issue would contract an IT person (you) with no experience in Access, vba or macros. That is not meant to be negative to you, it is a question of managements approach to data management/discipline.
Enough soapbox. Send us what you can for more focused responses.
I sure hope you're also contracted for:
-some documentation including
-a practical overview of the components
-details of each table and form
-guides for operating this application including backups
-a list of things (shortcomings as well as great points that should be familiar)
-some longer term maintenance
Good luck.