Not really a question, but posting this for comments because I don't recall seeing this approach before. I was responding to a comment on a previous answer, and tried something I'd not attempted before: the result was interesting so I though I'd post it as a stand-alone question, along with my own answer.
There have been many questions here on SO (and many other forums) along the lines of "what's wrong with my user-defined function" where the answer has been "you can't update a worksheet from a UDF" - this restriction outlined here:
There are a few methods which have been described to overcome this e.g. see here (https://sites.google.com/site/e90e50/excel-formula-to-change-the-value-of-another-cell) but I don't think my exact approach is among them.
See also: changing cell comments from a UDF