The tricky bit here is, you don't know the exchange rate. Even if, on the currency conversion screen, they display a rate, it's "indicative".
I asked support, and they told me that - to know the rate for the day - I have to call their office in the morning after 930am and ask.
Are there any low or zero commission brokers for US stocks that allow for pre market and after market trading?
In any case it's best to check with a brokerage directly.