Automatic currency conversion on checkout

Convert Euro currency to US Dollar amount and update payment gateway amount to charge US Dollars. Site uses EU currency throughout the cart process, [login to view URL] processes CC transactions in USD only. Current setup: On submission of form a php page is called containing the order total amount and redirects to [login to view URL] checkout form, the value populated is the Euro value without conversion. Desired Solution: On submission of form before redirect to [login to view URL], a shadow box needs to appear showing the user there is a currency conversation occurring. Then after a set time of 3 seconds the shadow box closes, the function to convert currency is called and XML updated for [login to view URL], and then redirect to [login to view URL] with US price appearing in form. Required Results: 1. on submitting form show shadow box 2. show shadow box that is timed out and then closes 3. submit form A. Update amount passed to for billing B. calling PHP function to redirect to [login to view URL] with new set amount 4. Redirect shows US based currency