Using Different Income Account During a CreditMemo/Return

When a return (or credit memo) is issued I would like the items on the credit memo or return authorization to use a different GL account than the income account specified on the item.

For example, if item 40010 has Gross Sales of $100 (10 boxes @ $10 invoice price) and one customer returns one box for a return refund of $10, income statement should show a view like this:

40010 Gross Sales   $100
Returns                    ($10)

What's the best way to implement this flow?

Thanks!