Change sign of currency? NO number

[gs]

Hi, how I can do to make the change currency's sign(blockcurrencies), I mean:
The dollar price is USD 255
The change I want to do with the exchange rate is just the sign, then it would be as follows:
The euro price is € 255.

How could you do that?
Or to create a button to do that, you change only the sign, not being the blockcurrencies.

Thank you !
Sorry for my bad english.