Multi-Currency transactions in Microsoft Great Plains

I need some advice on how to process multi-currency transactions in GP.

1. Currently our product always sends a transaction thru to the Gateway using the Originating Currency

a. This is why a customer who creates an invoice for 1.26 Euros is charged $1.26

b. Customer are currently manually settling multi currency transactions in GP which is very inconvenient for them.

c. We came up with a solution that if we submitted all transactions using the Functional Currency, it would ease all the inconvenience.

i. This sounded good at the time but further discussion led us to the conclusion it would need to be a configurable option.