I'm trying to create a table with 3 columns:

1. Expression 1 --> =Count (ID) Where Month = User selection

2. Expression 2 --> =Count (ID) Where Month = User selection

3. Result --> =Expression 1 - Expression 2

Month in table 1 and table 2 are variable and should be selected by the user.

The goal is that the user can decide which months he wants to compare.

Any tips how to build this?