I hope my title is understandable :O ;-)
It is quite tricky to schedule the publication of a new version. The straight forward approach is to put that function at the same spot where the first publication date is set. Perhaps one more button beside or somthing else simple.
Now you have to perform a stream of "tricks" to achieve the target. And most of these operations are not intuitive at all. Read more at http://world.episerver.com/Templates/Forum/Pages/thread.aspx?id=34300&pageIndex=1#reply