Is there a way to track total mission playtime?

Starcraft 2: Wings of Liberty has an achievement to complete the campaign on Normal in under 8 hours. I've already seen this question: How do I earn SC2's "Hurry up, it's raid night" achievement?, which lists how to earn the achievement, but is there any way to track how much time in total has been spent?

Or do I need to go to the mission screen and add up all the times manually?

I"m just thinking it may be easier to replay a mission for a better time (by reloading a save from before that mission), then it would be to get through the entire campaign to find out I missed by 10 seconds or so.