I am trying to set-up base for tracking some financial information.

Can someone help me with how to do this (I might be missing something obvious or it may be can’t be done :D). I will try to simplify it so it’s clearer.

I have two fields A & B and Status. Everything that I will explain happens in same record.

I will use column B to write amount to be paid. When someone change status to Paid, I would like to input value from B into A, after which I would reset the status and “empty” field B. Then I would enter new value for B and when status is again changed to Paid, I need it to add new value of B to previous value of A (basically B=B+A). I need this process to repeat multiple times (every time someone enter new value for B and change status to Paid).

I hope this is clear enough so you can understand. If something is unclear, I will try to explain it in more details.