SUMIF in discontinuous range with possible #N/As

You could use

Formula:

=SUM(IF(ISNUMBER(N(OFFSET(A1,0,{0;2;4}))),N(OFFSET(A1,0,{0;2;4}))))

Originally Posted by Bob Phillips

You could use

Formula:

=SUM(IF(ISNUMBER(N(OFFSET(A1,0,{0;2;4}))),N(OFFSET(A1,0,{0;2;4}))))

Thanks. This works well. Out of curiosity, why is N() necessary, for example in front of the offset? As I understand it, N just returns the number if it is a number, and the error if it is an error, so why not go directly with ISNUMBER(OFFSET ? I tried it and it didn't work, so it seems N() is necessary, but for what reason? Is it because due to programming limitations it needs to somehow "convert" from the array created by OFFSET?