Get percentage correct when using pivot table Nprinting

[qliknewbie_1]

Hi,

I have a straight table that I'm converting to a pivot table in Nprinting to get subtotals. Doing this works fine when filter is set to show one sheet pr (my case ID). I'm also trying to have a front sheet showing a total for all ID's. Everything is working fine, except for my precentage. It seems to either take the sum of all ID's or if I use average it will take the average percentage instead of just = 'current yr sales' / 'prev year sales' -1. 
I've tried adding a calculated field, but that throws an error. Does anyone know how to solve this?

Thanks so much!