Compare reports over time

I have a number of excel reports that are generated every fortnight.  They detail all the positions in my organisation as well as the pay rate, job title, occupants etc...

Our finance team are taking a greater interest in these and would like to be able to report on significant changes between any two reports for magical finance reasons.

I would like the capacity to have a Power BI dashboard that allows them to select any two dates of these reports and show each position that is new, or has had a change to either title and cost centre in comparison to the previous report.  Conversly this could work backwards and show positions that WERE in the old report, but are not in the new report.

I can figure out how to do this by uploading each excel document seperately but I'd rather have a mechanism that means I can combine all the docs in the folder and work from one long table.

Any thoughts?