Try this

=SUM(IF(MOD(COLUMN(G12:IV12),7)=0,G12:IV12,0))

This is an array and must be entered with CTRL+Shift+Enter.

Mike

"Igorin" wrote:

Hello,

How do I write a function that adds the values for the intersection between
row 12 and every 7th column (to give a concrete example) .

To illustrate:

Add the cells G12, N12, U12, AB12, ...

Can somebody give me an idea?

--
igor