Gain or loss on premature settlement

Dear Experts,

While posting the gain or loss entry in TPM18 for Premature Settled contracts, the system is picking the Exchange rate from OB08 table, instead it should calculate the gain or loss based on the original contract booking rate.

For example:

I have booked a forward contract at INR57 for USD/INR with maturity date - 31.03.2013.

I am cancelling the contract on 28.02.2013 at INR55. When I do a premature settlement, I enter the cancellation rate and the value date as 28.02.2013.

Now there are two transactions created i.e. 105 and 103.

While posting the gain or loss for transaction 105, the system calculates the gain or loss based on the exchange rate on 28.02.2013, but instead it should calculate the gain or loss on the booked rate which is INR57.

I know the round about solution of maintaining the forward rate i.e. INR 57 in Edit Flows under Cash Flow tab.

But why the system calculates the gain or loss based on the exchange rate prevailing on the date of cancellation, instead of picking the original booking rate automatically?

Is there a way to automatically populate the original rate in the 105 contract?

Am I missing any configuration?

Regards,

Kamal