RangeSum - not working?

[#1]

Can anyone help me with this expression, which doesnt seem to be working

Col 14 is a sum based on another 2 expressions. I need to show an accumulation of 12 months but cannot use the accumulate function as I need to do a further calculation.

Any ideas?

Thanks

RangeSum

(below(Sum(Column(14)),0,12),YearMonthName

)

[#2]

Can anyone help with this problem

- many thanks