There is one flight leaving for ottawa at around 1:15 pm Vancouver time. If you rush it, you may have time to get on board. In fact, you should book the AC138 arrives at 10:45 PM but if you can make it to the Air Canada counter at 12:00PM, you can ask them to transfer you to the earlier one. Of course, if doing that, you have to take your luggages before hand. Also please note this is not an everyday flight so check out with ac first.