General Ledger PLD

Hi,

I use a system variable to show Debit/Credit Amount in our General Ledger PLD, on the criteria selection of the General Ledger there's an option to sort those Debit/Credit fields ascending or descending, our Local Currency is set to USD, so, the amounts in Foreign Currency are differents depending on the Rate, the question is: ¿How can I sort the Debit (FC) and Credit (FC) Amount on my PLD?

Thanks.