GetNthRecord can be used to access data from the previous record, but I prefer this approach which I've used for years with a debit, credit, running balance "ledger" system like this:
Define a calculation field, cBal as:
Income - Expense
Then define a summary field, sBalance as the total of cBal and specify the running total option. cBal need not be placed anywhere on your layout and sBalance is the field you'd put in your "E" column position on a list or table view layout to get the desired result here.