How to use prior function in case of year change?

@prior

Hi,

I am using @prior function to get previous month's actual. It is working fine for Jan to Dec period of the same Year.

Ex.

For Period Jun and Year-FY15 , Prior of 3 period returns correctly as Mar-FY15 but for Period Feb and Year-FY15, simple prior would not return anything.

I was thinking to modify the formula so that if month is Feb then create a formula which will return period as Nov and use prior function for Year.

I am not sure this is best way of defining formula.

Please let us know best practice.