# Reverse Cumulate Alternative?

Hi - hoping to see if anyone has a solution to this:

In the following example, I'm trying to calculate (going backwards) when the sum (less current period) would be greater than the test doh line item.

In Jan 20, it would look back 3 periods to be greater than or equal to 92. (Oct/Nov/Dec)

In Mar 20, it would look back 4 periods to be greater than or equal to 92. (Nov, Dec, Jan, Feb)

I have tried various forms of CUMULATE, OFFSET, PREVIOUS... but haven't been able to create this logic.

Has anyone had success performing a reverse recursion?

Jack

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• one solution is: test all possibilities with a movingsum and a numbered list:

extracting the result  with first non blank:

here's the list of possibilities:

there might be an easier way if we are really talking about calendar days and simple numbers.

but this solution will work for anything.

• Looks like a workable solution. thanks

• You could use that start date and period() function to find which month satisfies the 92 days prior. using a month period line item your formula would be Period(start() - test doh)  from here you should easily be able to calculate how many months to look back.