Hi Phil,
Thanks for taking the time to create a detailed specifications document; it makes life so much easier when you know the scope from the start.
My first question is, why Excel? Spreadsheets are generally most appropriate for: data analysis, calculations, statistical comparisons, etc. Databases work well for: data management, complex searches, multiple users, displaying data summaries and reports, etc. Although you can make pseudo-relational databases using spreadsheets, it's kind of like thinking you can make a hammer from a shoe; you might be able to get it work, but you're better off using the right tool for the job from the very start.
A long while ago now, I (and another officer) wrote an Access database which tracked correspondence at a military headquarters. It was a lot more complicated than your requirements, but it was so successful that it was picked up by other headquarters; it eventually became the basis of a much larger project which spread almost Defence-wide.
If you don't have Access, you could use any other database system. You might consider a "cloud" based solution where the registry is stored on a web-server (protected, of course) so you can access the data from "anywhere, anytime" using a web-interface. If only one user requires access to the data, mySQL/MariaDB (and other databases) can be locally installed for free.
Anyway, you've probably read enough from me. If you want to get in touch to discuss the possibilities...
Scott
Perth, WA