Determine period and year from a cell value

Hi all,

Please have a look at the image below:

If you look at column F (CPI), FY21->M2 has a different value from the rest of the cells in the column. The users asks us for a way so calcs can detect that value is different from the rest and is must be spread from there across all future periods and years (i.e, FY21->M3, FY21->M4, ... FYXX->M12).

I'm in need of good ideas. I'm able to extract that value (see column G) and I can store it somewhere else so I can reference it in a