On Thu, 28 Jul 2005 13:07:22 +0100, Richard Buttrey
<chaos.theory.nospam.removethis@zen.co.uk> wrote:

>Ron,
>
>My apologies for confusing the matter. I should have referred to
>column K rather than column C
>
>Thanks for your input.
>
>Rgds

Oops, I saw your subsequent posting and see how you want to determine 1, vs
1&4, vs 1&4&7.

Assuming you're being quite specific, the following formula should do what you
describe:

=SUMPRODUCT((COLUMN(B1:J1)<=CHOOSE(A1/3,2,5,8))*
(MOD(COLUMN(B1:J1)-2,3)=0)*B1:J1)


--ron