=SUMPRODUCT((MOD(ROW($AG$1:INDEX($AG:$AG,9*(ROWS($AG$1:AG1)-1)+4))-ROW($AG$1)-3,9)=0)+0,$AG$1:INDEX($AG:$AG,9*(ROWS($AG$1:AG1)-1)+4))/SUMPRODUCT((MOD(ROW($AG$1:INDEX($AG:$AG,9*(ROWS($AG$1:AG1)-1)+4))-ROW($AG$1)-3,9)=0)+0,($AG$1:INDEX($AG:$AG,9*(ROWS($AG$1:AG1)-1)+4)>0)+0)