Hi again,

You can alter the formula to
=SUMPRODUCT((MASTER!$R$5:$NS$5>=C$2)*(MASTER!$R$5:$NS$5<D$2)*(MASTER!$D$6:$D$87=$B29)*IF(ISNUMBER(MASTER!$R$6:$NS$87),MASTER!$R$6:$NS$87,0))
which must be array entered using Ctl+Shift+Enter and then filled down and across.