I'm trying to find all the people in my spreadsheet who have given
donations for 12 consecutive months in the last 60 months. I know how
to do a simple count of all donations in the last 60 months, but I'm
not sure how to write a formula that will identify those who gave
consecutively for any 12 month period in th last 60 months. Any
ideas?
This is how I have my spreadsheet formatted.

Name | Month1| Month2| Month3| Month4| | Month5| | Month6| |
Month7| | Month8| ...
Johan Doe| $10 | $5 | $0 | $100 | $100 |
$0 | $10 | $10 |