AX 2012 Ledger Exchange rate service

Hi,

I have a requirement to import Exchange rate using standard Ledger Exchange rate service available in Ax2012.

I am using Create action, but however when Import the currency pair let us say USD to GBP first time with exch rate 0.814 for 24th April 2013 it imports correctly as this currency pair did not exist in the system.

Later when I import the same as above for date 25th April, the system throws error saying the currency pair USD to GBP already exists.

Have anyone used this service and can share some info of how they have used?

Thanks,

Ismail.