"Mutcluck" wrote...
How can I Sum

A43+A83+A123+A163 into infinity.
....

Two ways.

=SUMPRODUCT(--(MOD(ROW(A43:A65536),40)=3,A43:A65536)

=SUMPRODUCT(N(OFFSET(A43,40*(ROW(1:1638)-1),0)))

The latter does less work.