>Yes, I know about the real exchange rate is when we process the payment. But, I need to have this as close as possible to the actual rate when the payment will be done. So, if I have it ok at every 5 minutes, for exemple, this will be good enough for me. It was just surprising for me to learn that this is changing overnight as well when the markets are closed between those two countries. I was trying to understand what could affect that.

What "big" corporations do is use the exhange rate posted at close of day the transaction was posted, or close at day before.

Can your merchant account service do the conversion for you?

>But, the most important issue is why this value returned by the Web Service was different from two different routes. I mean, the value were not close at all. The Web server located in Montreal returned something like 1.1502 to 1.1515 for about an hour. But, my PC in New Brunswick, was returning always something like 1.1530 to 1.1534 during the same period.

Cheap data. Real time rates are expensive - you have to have a Bloomberg (or something similar). The cheap rate services can lag the market by minutes hours or day.

Whay are you using soap? Are you page "scraping"? How is the return data packaged?