I
I go onto the Disney gift card site and see what the balance of my card is in USD - it usually displays the USD balance. You would have to register your card for this to work. Then I go to the
DCL site and put that amount as payment.
If you are only paying a portion from your gift card, you would have to divide the display amount (USD) from the CDN balance and find out what exchange they are using.
I hope this helps!