This is a feature that I believe a lot of us would like to have, and is my only major complaint about the product. Even if you could get your Replay to sync at a certain time, you still have the issue of the MyReplayTV web site which prevents you from scheduling recordings prior to 6am the following day. If they lifted that restriction, I think that it would be easy enough to write a utility which would allow you to access your ReplayTV from work and force it sync.
I wrote a long email to various departments at SB voicing my complaint. It seems to me that SB has gone out of their way to prevent users from remotely scheduling a recording even though they list this as one of the benefits of their product. In fairness to them, they did tell me that this sort of functionality is planned for the near future, and the ability to do frequent checks for changes to MyReplayTV is something that has already been built into the 5000's, but is not yet activated. I suppose that if enough of us complained, they might bump up the priority of completing this enhancement.