If A1 0 AND SUM(A2:A12) = 0 then A13 = Jan
If A2 0 AND SUM(A3:A12) = 0 then A13 = Feb
If A3 0 AND SUM(A4:A12) = 0 then A13 = March
etc.etc.

Rather than just using nested Ifs which is cumbersome I am trying:

Function Month(Integer)

Select Case Integer
Case a10,sum(a2:a12)=0
Month = "Jan"

etc....

help is much appreciated - thanks