You're right, of course. The problem in the R&R case is not with Excel itself, but that it's being used with a lack of rigour. If it were being done in C# or R

You're right, of course. The problem in the R&R case is not with Excel itself, but that it's being used with a lack of rigour. If it were being done in C# or R I would expect unit tests and so on. I'm not saying that would make such a mistake impossible, but programmers have processes and tools for a reason. In the OPs case the problem actually is with excel though.