Kate, I am copying and pasting something from another host I used. Hope it works for you, too.
I don't quite understand the second paragraph she wrote, but perhaps you do.
- On your calendar
Availability Settings > Reservation Preference (top right)
go to: Add another requirement (bottom right)
In the popup box select "specific dates" from the "During" drop down dates
- Only problem is that you can't have two different settings on consecutive nights, as the "rules" works on days not nights, so for a Monday night you put in the dates for between Monday and Tuesday, But then the system won't allow Tuesday to be used again to make a different rule for Tuesday night.