Change convertECB.php

[marvays]

Hi.
On one website i need change convertECB.php . . . . How Can I make it?

I have hungary eshop and slovak owner. This owner selling products for hungarian people with forints. But need invoice calculate in euros.
I am using Artio Invoice, where i can use forints in invoice, nad I can display summary like euros. Its ok. This summary calculate with convertECB.php . . . . but i need calculat like slovak central bank.
Can I any way change it?