Count of Rolling Months in Denominator

[rsdhavle]

I am calculating expression based on rolling 12 months, so lets say i have data for 2 years 2015,2016. I want to divide my expression in denominator by 12 till i have data for 12 months available with me however when i am selecting month Nov 2015 i want to divide it by 11 as i have only 11 months rolling data available and when i am selecting Oct 2015 i want to divide by 10..

How can we calculate this count of month dynamically based on a range of rolling months available?

[Gysbert_Wassenaar]

Perhaps: rangemin(12, rowno())

[rsdhavle]

it is giving me 12 for all selections even if i select 2015 Oct, September etc.

[sunny_talwar]

Would you be able to share a sample to show what exactly are you trying to do?