excel formula to add every 4th column

[alwinaz]

Hi there

How do i edit the following formula to add every 4th column in excel?

=SUMPRODUCT(MOD( COLUMN(B9:ABK9),2 )*B9:ABK9)

[daddylonglegs]

I always use this syntax

=SUMPRODUCT((MOD(COLUMN(Range)-MIN(COLUMN(Range)),n)=0)+0,Range)

assuming Range is a row of values that will sum the first entry followed by every nth, so if you make it specific like

=SUMPRODUCT((MOD(COLUMN(B9:ABK9)-MIN(COLUMN(B9:ABK9)),4)=0)+0,B9:ABK9)

that will sum B9, F9, J9, N9 etc.

adjust ranges as required