Hi there -- I downloaded the file, and what you've put together is JUST what I needed. (I should have been clearer about the empty columns -- they will never have dates.)
THANK YOU so much for taking the time to help me with this -- I really appreciate it! But the person for whom I'm putting together a scheduling spreadsheet will appreciate it even more: an 80-year-old who still works full-time, brilliant but completely distracted, constantly double-booking himself. This will provide a bit of functionality he asked for that I wasn't able to figure out.