shorthand for consistent but non-contiguous range of cells

[Julz]

is there any way of specifying a range of non-contiguous cells? E.g., if I
wanted to sum every third cell, rather than going =SUM(A1,A4,A7,A10) is
there any notation I could use analogous to =SUM(A1:A10)? I'd prefer to
avoid macros in this instance if possible.

This would be for a large spreadsheet, to which extra rows are sometimes
added.

thanks,

Julz

 

[Jim Rech]

Here's one way to do it although it's no pleasure to look at. This adds
A11, 14, 17 and 20:

=SUMPRODUCT(A11:A20,(MOD(ROW(A11:A20)-ROW(A11),3)=0)*1)

 

[Julz]

Hmm - may not be pretty but if it does the trick that's what matters. Many
thanks! J