Recognize single digit number as month for subtraction

Hello,

I have data coming out of a system where the month number and year are coming out in two separate columns. Example: One cell has a 3 and the other a 16. For calculation purposes there is another field that shows the number 4. 4 represents the number of months to count back from 3 in order to grab a CPI index to calculate CPI increases. The issue I am having is if I subtract 4 from 3 I get negative 1. I need to take 4 away from three to get 11 (November). So that the calculation will grab the CPI index that was reported 4 months before the 3(March). any suggestions? If it were farther along in the year it would work fine. It is when it crosses years that it becomes an issue and the fields are not coming over in a date format where the subtraction would work.

Thanks in Advance!

Try

=MONTH(EDATE(DATE(2017,G1,1),-I1))

G1 = given month # (3)
I1 = number to subtract from month number (4)

Thanks. that formula worked very nicely. there are other fields to where I can get the 2017 to be formula driven too I suppose.

ChemistB...Your formula works as well but without the +1 in it. The plus 1 makes the number 12 and I need it to be 11. Removing the plus 1 gets me to 11. Both formulas seem to work nicely.

awesome. thanks again to you both.

Chemist's formula needs the plus 1 because month 4 - 4 would equal 0, there is no such month as 0.

I think that should be
=MOD(B5-5,12)+1