is this what you are looking for.
I get the numbers with
if first() != 0 then
if ATTR( [Months] )%6 = 1 then SUM([Value]) / lookup(SUM([Value]), -1) end
Basically, except for the first month, for every 7th month (modulo 6 = 1) then divide the current value by the value of the precedent row.
Ratio_Calc(mc).twbx 27.0 KB