Quick question:

In a table with lots of operations in which I have unique identifiers (concatenating date and operation ID), how can I choose to calculate the change between the amount of one month and the previous one? (Assuming that the rows are never next to each other since there are lots of different operations and dates).

Specifically, telling the code to take the amount of the row with a specific date and operation, and substract it from another specific row with another date and operation

Thanks in advance!