General :: Database Redundancy And Validation

I've inherited a database with multiple users, massive redundancies, and strict policy limitations:

1. The existing table structures must remain, despite redundancies that create problems constantly, because of multiple client programs.
2. Data entry must not be programmatic: no data can be generated by code.

I can, however,
A. Create new, interdependent tables, or
B. Validate data with criteria or VBA.

I have two rules I'd like to enforce:

Rule 1: This one is easy. Certain redundant Locations must be identical. So, all the Locations in Table A must appear in Table B as well (although B may contain Locations not in A). No Big Deal.

Rule 2: An absolute rule for every Location is that each must occur between the boundaries established for that particular Track and Section.

So, given that I have a Table with Records of Track, Section, StartLocation, EndLocation (which defines the limits for Location values)...
Track 1, Section 1: Starts at Location -100, Ends at Location 100
Track 1, Section 2: Starts at Location 50, Ends at Location 20
Track 2, Section 3: Starts at Location 0, Ends at Location 400

I want to prevent users from entering illegal locations in another Table with Track, Section, Location, like:Track 1, Section 1, Location 101 (this location is beyond the end of Track 1 Section 1)I could code this in VBA, but the downside is it won't be enforced if the user has Macros turned off by default.