Cenvat credit for excess payment of ed

DEAR ALL FRIENDS, DO U TELL ME ? IF I HAVE PAID EXCESS DUTY IN PLA ACCOUNT OR DEBITED TO CENVAT CREDIT ACCOUNT WITH WRONGLY ASSUMING THAT EXPORT SALES IS REGULAR SALES, THEN SHALL I SUCH EXCESS PAYMENT CREDITED IN THIS MONTH OR APPLY FOR REFUND FOR EXCESS PAID DUTY ? WHICH IS THE SOLUTION? PLEASE TELL EARLIEST.