Somewhat-complicated Workflow

Hi,

I'd like to let two users set up an appointment on a certain date and time. This would be done with the Workflow module, I guess, because there are different states like (Pending) and (Confirmed).

I set up a new content type called "meeting." The fields include a nodereference to the other user in the meeting and a date field. I am having a hard time thinking of how the transitions will work, though. There needs to be a way for both users to confirm a date and time. So, access to the node should be limited to those two users.

Thanks for any help,

-Ben