One way

=SUMPRODUCT(--(MOD(ROW(D1:D30),3)=0),D1:D30)

will sum D3,D6, D9 and so on


--

Regards,

Peo Sjoblom


"Ken" wrote in message
...
I have a fairly large spreadsheet. In a particularl section I would like
to
sum the values contained in every third cell. Currently I have over 30
cells
I would like to sum and the only way I can find to do so is by referencing
each cell individually with a + sign in front. All of the +cell references
is
cumbersome and inefficient.