It's not possible to book a specific fare but to get a list of all the fares:

Go to www.travelocity.ca ; under travel tools on the right, there's an option called 'Fare listings'. You might need to register before you can access that (but registration is free).

Or

http://www.expedia.ca/pub/agent.dll?qscr=ftap&rfrr=-983 If you want to see transborder or domestic AC fares using this, you will have to leave airline preference as 'all airlines' because if you select 'Air Canada', the fares won't come up. As a result of this, the list is not as complete as using the travelocity option. You could select Air Canada if you're looking at international fares, it will come up.

Feel free to ask if you need more help.