You'd post a pic of your db relationships in a new thread and at least link to this one for explanations of the business. Might even be better to just copy/paste what's relevant about the explanation into your new thread just to keep everything tidy and together. However, I know nothing about Azure and can only guess that you can migrate these tables (or at least repeat the structure) to it.
I don't see an issue with the data being in Excel as there are several ways to get it into Access. If that data is manually input, why not get rid of the spreadsheets and input directly into Access, either into your linked Azure tables or ones local to the db? Same if the Excel data is pushed or pulled from another application rather than being keyed in. Just go directly from that app to Access and simply the whole process?
As for your last question I can't really relate to what you're saying even after I review the above. Perhaps I'm missing the part that explains it, but my eyes just start glazing over when I read a lot of unfamiliar jargon. Must be an age thing. Are you saying that some thing has a cost but the current cost depends on a date range? The cost data needs to be historical as well?
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.