Ok - cool. You do understand currencies though dont you? And the fact that currencies change and are related to various stock markets/interest rates blah blah??
So - the first thing you need to do is source somewhere to provide you with the latest exchange rates via some regular update method (several times a day would be about right for something that should reflect real numbers). These do exist (Thomas Cook etc use them) but I have no idea where you would start.
I have a feeling that wont be cheap though 🙂 After that - it should be a piece of cake!
