Working the currency exchange is horrible

Let me just do the math in my head. It just keeps constantly changing itself when I'm trying to sell stuff. When you are selling stuff, often times you can sell for more if you see how much it is if you were to buy it.

So it just keeps changing itself back after I input the price I want to sell for and then instantly changes as I'm tyring to press submit, already ripped myself out of some currency.

Is there a setting for this?

I don't need you to do the math for me, it's basic math.