The answer depends on how you are computing your Cash Flow.
If you are computing the Cash Flow dynamically (DynamicCalc members), then for each of the two cash flow members that could receive the loan account balance, you will need to retrieve the source loan account balance, and depending on the signage, return the value or return nothing.
If you are using stored calculations (be it FormulaPass or BusinessRule), you would need to obtain the source loan account balance, and based on the balance write to one or the other Cash Flow line. If you know how to use data buffers, this can be handled quite efficiently.
With stored calculations, there are few other options too, depending on how creative you want to be and how you might be computing the bulk of the cash flow.
