Being able to write functions doesn’t make a language functional. The hallmark of functional programming is closures as first-class objects, passed as arguments

Being able to write functions doesn’t make a language functional. The hallmark of functional programming is closures as first-class objects, passed as arguments or returned from other functions. The nearest Excel equivalent would be constructing a formula string for later evaluation, which is far from the same thing. If you wanted to perform lambda calculus in Excel you’d end up implementing your own functional programming language in VBA. Have fun with that :-)