Surely, when you start getting to the realms of datasets with more than 65k rows, a spreadsheet is not the right repository. You need a database solution (Access maybe) or a flat-file solution.
Unless you're telling me that the recipient of a multi-sheet Excel file containing several-hundred-thousand rows is actually going to build multi-sheet analytics on it, or is an accountant (!), this requirement should be reviewed asap, in my opinion.
Go ahead - prove me wrong :-)
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