Robin,

Something like this, array entered (entered using Ctrl-Shift-Enter)

(this formula in cell L1)
=SUM(IF(MOD(COLUMN($A$1:K1),4)=0,$A$1:K1,0))

HTH,
Bernie
MS Excel MVP



"Robin" wrote in message
...
I have designed a cashflow forcast and need to be able to extend it easily.
for each month I have 4 columns and one is a the cumlative of another of
the
4 columns in all proceeding month. I am tryong to find a way of easily
extending this by filling across. the problem is it needs to add evey say
forth column on the left and as you fill across it needs to extend the
formula. This formula is only in every forth column itself ie there are
other
formulas between itself and its repeats. I can fill across but my problem
is
getting it to automatically extend.If I do it manually it takes ages. Any
help would be appreciated