Impact of exchange rates on import/export

Just a quick thought, what impact does a rising exchange rate have on the import/export potential for a country?  For example, CAD has been appreciating against the USD for some time and if the Bank of Canada is unable to derail this appreciation, what impact does it have on Canadian exports? 

For example nearly 76% of Canadian exports as of 2008 go to the US, a rise in the CAD/USD exchange rate makes those exports more expensive decreasing demand.  This while only 63% of Canadian imports come from the US as of 2008, meaning while imports get cheaper, demand many not increase due to lack of exports and their trade surplus would decrease.

The next question to answer would be what impact this has on the CAD and Canadian markets long term?  Further, how will Canadian exporters perform over coming months if appreciation continues.