SAP IBP for supply - Avarage of last periods

Hi, Experts

i would like to know how could i perform an avarage ("calculation") of the last "8" time buckets periods from a particular keyfigure, assuming that i am in IBP for supply license and i can not run move avarage statistical forecast, i don´t know the correct sintaxe to apply an avarage of the last time buckets and there is no documentation available to do it.

Thanks!

Fábio Matias