Sumproduct of shifting array with a left boundary

[svalentine91]

So I have dates at the top

have a line that needs to check if month = 11 and then sum the array of the last 12 months.

Having trouble with the leftmost boundary, as explained on sheet.

Thank you!!

[Fotis1991]

In B8 and copy across??

=IF(MONTH(B2)=11,SUM(A$3:$B6),"-")

[benishiryo]

hi svalentine91, if you have more than 12 months, then 1 way:
=IF(MONTH(B2)=11,SUM(OFFSET(A3,,,4,-MIN(12,COLUMNS($A3:A3)))),0)

[svalentine91]

Thanks for the reply, but looking back I was not clear enough. I have a model that changes; When I enter a specific date, say 01/01/2013, Case 1 will be returned, albeit continuing on into future years

If I was to enter 08/01/2013, case 2 would occur, once again to an nth date.

Now, the first column, column B will change, and sometimes there will not be data for the last 12 months.(In case 1 there are only 10 months of data, in case 2, only 3 months)

my question is to find the sumproduct formula that would fulfill the given requirements, finding the sum of the data in the number of months, max 12 until it hits the leftmost boundary.

[svalentine91]

hi svalentine91, if you have more than 12 months, then 1 way:
=IF(MONTH(B2)=11,SUM(OFFSET(A3,,,4,-MIN(12,COLUMNS($A3:A3)))),0)

thank you very much