POS: Advance amount

Hi all,
When using POS, if a customer paid extra Rs200 against invoice amount Rs.1800. That 200 will be the first show in the change amount field which will be given back to the customer.
Is it possible, if we do not return that amount to customer and record that amount as an advance for that customer, so that next time we will adjust that amount in his invoice.


POS is cash and carry only. Use Sales Invoice for everything else.