Exclude specific dates from word count target

I searched the forum for this and couldn’t find anything relevant; apologies if it’s been covered before.

I would love to be able to exclude specific dates from the daily session target calculator.
It’s a common enough situation, I think: I normally write Mo-Sat, but sometimes I know I’ll need to take extra days off (birthdays, holidays etc), so it’d be really useful if these could be counted as non-writing days as well when calculating the session target. Does that make sense?

Thank you!