How to create a financial report showing 12 months rolling back

Summary:

I need to create a report that always shows data for 12 months period back starting the choice made on a prompt for year and period

Content (required):

So, if I choose on prompt Year=FY21 and Period=Aug, the report have to show those columns:

Sep-FY20 Oct-FY20 Nov-FY20 Dec-FY20 Jan-FY21 Feb-FY21 Mar-FY21 Apr-FY21 May-FY21 Jun-FY21 Jul-FY21 Aug-FY21

if I choose Sep-FY21, the starting month shown will be Oct-FY20, and so on.

I would like to use some FR functions to help me, could you suggest me some solution? I don't want to use substitution variable, ma only FR functions.