Issue in Vendor A/c clearing

Hi

We have an issue in which we have paid some advance to vendor in EURO at a certain rate say 1 EURO = 1.25 USD. Now at the same rate we have booked the vendor invoice in USD because the bills from vendor have come in USD. Thus both the down payment and invoice are shown of same value in INR when we view the items in FBL1N. But when we try to clear the vendor account the system is picking the rate maintained in exchange rate table, thus showing a difference in invoice amount in INR. How can we clear the open advance in EURO against the vendor invoice in USD, when actually there is no change of rate?

Pls help

Regards

Rahul