Prevent US buyers from checking out in Canadian Dollars (only US dollars)

Question

My store has two currencies, US dollars and Canadian dollars. Base currency is Canadian dollars, US dollars is just a conversion. But I have an extension which allows customer to checkout in the currency they wish (CAD or USD) and the credit card will be charged in the respective currency.

Is there a way to prevent US buyers from checking out using Canadian dollars ?

Thanks all in advance!

Answer 1

You could try an extension that only allows them to checkout in the currency of their region.

http://www.magentocommerce.com/magento-connect/auto-currency-switcher-1.html