Excel is a disaster. It will randomly corrupt input that happens to fit certain patterns by parsing it into "dates" or "numbers", unless you go to the trouble of explicitly setting the right "cell properties" via the incredibly clunky UI. It hides the code that's input in cells, lets it randomly mix with input data and does not support any kind of source control for it. It's not even fit for purpose as a prototyping tool, you're literally better off writing some code in FORTRAN IV and key-punching it into a fresh deck of punched cards. At least you're going to have proper code/data separation.