Page break in matrix

I've have a matrix that must, if it has more than 3 columns, add a pagebreak after every 3 columns. I've searched the Internet, and some of the things look promissing, but I can't make it work.

One of the things I did, was adding a parent group on the expression Field!NumberOfRow.Value Mod 3 and checked the box for a pagebreak on this group. Nothing.

I saw a post somewhere that included the listbox with this matrix added, but it wasn't clear how to do it.

Can anyone help me?