Elaine - I think the biggest problem you're going to run into is the time differences. I'm not finding many options that will allow you to leave that day and still get there in time for CVW at 5ish. But flying out the night before ends up with having to find somewhere to spend the night. I checked quickly JetBlue, Air Tran, and Southwest for just a random April weekend, and can't find anything under $400 right now (for times that would work - I can find $200+ fares but they involve arriving late at night or leaving early in the morning going home, which would result in needing a hotel). One option I saw on Jet Blue was a redeye flight - leaving near midnight from CA and getting in near 11am, but then obviously you'd start out the visit exhausted. I usually use Orbitz for a comparison but know Southwest doesn't come up on that so check them separately as well. Good luck!
Edited to add that I also use Yapta to track fares, but my experience in the past few months is that the fares aren't changing much. I plugged in some for Orientation to Denver almost 2 months ago. I finally gave in and bought the tickets (more than I wanted to spend) about a month ago and the flights haven't changed at all since then in price. I'm sure it depends on the airline/day/location, but this is a site that at least will email you if/when it drops. Also Kayak is easy for comparing many flights and then sorting (or eliminating) the times/prices/locations/airlines you don't want to use.