Add certain cells based on a function

[MrSandman]

I have a column of data with several hundred rows. I want to add every other row and show the results in another cell. How would i go about doing this?

How about if i wanted to add every 2nd and 3rd row? Is there a function i can use to do this?

In other words:

1
2
3
4
5
6
7
8
9
10

I want to sum up the (2+3) then skip a row (5+6) skip another row (8+9) etc.

[davesexcel]

=SUM(IF(MOD(ROW($A$10:$A$19),$B$20)=0,$A$10:$A$19,0))

this is an array formula you will need to controll shift enter for it to work

$B$20 is the Nth value you want

Add every other number input 2 etc.