Add formula to pivot table or add data to pivot table to be shown in a graph

Hello everyone,

I have a pivot table that shows these results according my selected filters:

DEL 23
KAL 10
LAN 2
ZR1 12
ZR3 21


The things is, that I would like to have the results of what contains "ZR3" to be divided by 3, so, in this case I would like to have as a result for ZR3 to be 7 instead of 21. I tried to add a formula using "calculated field" option, but seems to be that it doesnt work when you want to put a condition of text as requests my need (something like "=IF(Customer="ZR3";nš/3;nš)" doesnt work.

I also tried to add the list in red with the desired results, but can not be added to the graph, because is blocked connected to the pivot table.

So, is there a way to add a formula into the pivot table to divide always the results of "ZR3" by 3, or to add the list with the red numbers into the graph?

PS: Note that the graph has to be always connected to the data of the pivot table, I can not make an independent graph just with the results of the list in red.