Cold Frame - Automatic Venting

[chris the bluebird]

I am thinking about buying a coldframe to help bring along my seedlings etc. I was wondering if anyone has fitted automatic venting/opening system to a coldframe? If so which one. The thinking behind it is that I am often away with work for a few days and I would have to leave the coldframe either open or closed which is not ideal.

Any thoughts or comments on the idea would be appreciated.