Multiple currency issue

Darsoononline

I have bank accounts in two different currency, the default CAD and IRR. When I pay from my IRR account, Wave automatically calculates the equivalent CAD value. However, since the exchange rate fluctuates a lot, that creates a problem. Since I have money in my IRR account, I only want payment to come from that account, so there is no need for Wave to convert currency back and forth which would only work if the exchange rate remains the same.