I have a rota worksheet that contains columns for start & finish times each
weekday and a final column that adds the total hours worked. I would like to
be able to enter text such as Holiday or Training in the daily columns but it
causes an error msg in the total hours cell.

I would like to asssign a value to the text, eg HOL would be considered as a
normal day - 8 hrs - and included in the total hrs.