How to schedule download of windows 7 updates?

To put it short: I'd like to schedule my windows updates to start/stop at certain times of day. How can I do this?
More explanation: This is because my internet traffic is limited by ISP and it's free only during a specific period throughout the day (2:00am-7:00am). I've set windows update setting to check for updates but notify me before downloading in order to prevent it from automatically using up my traffic. But then I have to manually tell it when to start downloading. I obviously don't want to stay up that late just to push a button.
So again, how can I schedule windows updates to start/stop at specified times?