Payment exchange rate by voucher line

Hello,

I have a question about the accounting of gains and losses calculated in a payment in foreign currency.

When I enter the voucher, it calculates gains and losses by receipt line, but the voucher has a specific exchange rate. When I enter the payment, the system writes a line of gains/losses regarding each line of the voucher versus the exchange rate of the payment, instead of writing one line per voucher.

Could anyone tell me if there's any set up that could be done in order to group the gains/losses of the payment in one line per voucher?