Comparing two cases

Hello everyone,
I need to compare two cases Cp distribution by extracting one to another. But when I try to use calculator, two case didn’t seem to get same calculator as variables. I am digging out for some python stuff but get nothing useful.
Thanks in advance.

Try the programmable filter. It can have multiple inputs which would be your two sources of which you intend to get the difference.

https://www.paraview.org/Wiki/Python_calculator_and_programmable_filter