You would have to update the site for this to work, but I suppose you could add columns for two different prices in two different currencies and allow the user to choose the currency they want to use. Then you could set a session variable with the currency selection and use the appropriate price based on the currency.
Or you could have an defined exchange rate and use math to determine the price based on the currency selection and a single price field.
It would be possible, but would definitely involve some amount of hand coding. It is something we could help with in a premier support ticket.