90 day tracking

[grizzly6969]

I have a spred sheet with a calendar from A12 to W87 =Jan 1 to Dec. 31
If john doe is absent I put an "A" in that date in the calendar
is it possible to have on sheet 2 lets say A2 turn red if there are 3 "A's "
in a 90 day period at any time through out the year

 

[JLatham]

First, please explain your calendar a little more. A12:W87 is 1748 cells.
That's a bit more than one year's worth.

Secondly, since there are roughly 275 contiguous 90-day periods in a year, I
can't imagine doing this without VBA. I don't think it's going to get done
with a formula using regular worksheet functions.