Convert platinum to gold

[Dacien]

Is there any way to convert platinum back down to gold? I have a quest that requires 23 gold, and he won't take 2 plat and 3 gold. I know because he greedily took it with no reward, which is so unlike the generous dwarven people.

Anyway, is this possible?

Edit: Nevermind, you have to click the currency coin from one slot and click it to the other at the bank. I thought only the "Change" button did anything. You can delete this thread.