Count last 7 days of pupil attendance that exceeds 31

Hi all


was after some help with an excel formula!!! does anyone know what formula I would use to adjust the starting point of its criteria for example if I had a spreadsheet of pupil attendance by day but then wanted a formula to show how many days I had 31 pupils in but only counting for the last 7 days(values)? so then each time I add a new value it would still only count back 7 days.
if the starting point was the same I would use COUNTIF(Sheet1!B:C,31) but how do I add only count the last 7 values without having to adjust the formula each time I add a value. as below

day 1 - 30
day 2 - 34
day 3 - 31
day 4 - 32
day 5 - 31
day 6 - 31
day 7 - 33

so when I add day 8 it would only count days 2,3,4,5,6,7 and 8. then when I add day 9 it will count days 3,4,5,6,7,8 and 9.

thank you in advance for any help