> Encoding data in cell formatting is questionable practice.
"Let's force the user to employ data-management best practices" is, for better or for worse, very much not the design philosophy of Excel. (More to the point, if you must consume the data that someone else produces, then you'd like very much to be able to deal with their less-than-best practices.)
"Let's force the user to employ data-management best practices" is, for better or for worse, very much not the design philosophy of Excel. (More to the point, if you must consume the data that someone else produces, then you'd like very much to be able to deal with their less-than-best practices.)