High level concept: Xlsx or xls? If it’s xlsx, stream the file, chunking 500 rows into each new file, watching for ref A1, then injecting that into previous f

High level concept: Xlsx or xls? If it’s xlsx, stream the file, chunking 500 rows into each new file, watching for ref A1, then injecting that into previous files. The xlsx format is a zip file of xml, not so bad to work with once you start. I should note, this works best if you don’t care about the order of the rows. They technically aren’t required to be in order (I think).