custom expressions in pivot table

[#1]

Hi everybody,

I tried to find an answer into the forum with partial success.

I have this pivot table, and i want to "customize" the XX column like this:

Column XX;

1° row = 93,1 % (51910 / (51910+3854)

2° row = 6,91% (3854 / (51910+3854)

3° row = null

.....etc....

before trying "hard" with all my expression I made this one to prove myself it will works, but nothing.

if(SeqVoci=1,Sum({<IdGruppo = {'2'}>} Importo))

as you can see into the 1°row of column XX there's a beautiful 0.

Thank you so much in advance