auto fill reference across documents

i’m a teacher and I class plan from a manual which has units. these units change everyweek for a single class but I also need to reuse some of them so I need to keep tabs on what I did and when, so as not to repeat myself too often. I need a global view of all the units I do each week for a given class in one document.

I’ve been doing this manually by creating a “master document” for each class where I update what I covered in that week so I can easily go back to it, but this is time consuming.

I thought of cross referencing (i know it exists but not quite how it works) but I think that is only for a single document. i need it to be across documents.

please help!!