>I am looking for a Web Service that will allow me to get the current exchange rate between CAD and USD. I need something accurate and not something that will return the exchange rate of the previous day. I looked at some Web site which provides this information. But, I need a way to have that automatically. One of my clients need that for their own store.

Check: http://www.oanda.com/site/converter-intro/ccc_intro.shtml
It's in real-time. Free and paid services.