Expression (Checkbook)

Just like in a checkbook, I want to create a query that contains 1 field
plus 1 expression:

- Expenses (field)
- Remaining Balance (expression)

Naturally, I want the Remaining Balance to be dynamically calculated based
on the previous record value in the Expenses field.

Example:

Expenses Remaining Balance
80
20 60
10 50


How do I do that in a query? If yes, how would such an expression look
like?

Also, how do I handle the first entry of $80 (beginning balance value)?

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Thanks,
Tom