Hello BSquared,
You can use the client side event for your date field, that will validate that it's two weeks at least when they select the date to order.
Unfortunately this could be quite a long script so I wouldn't be able to fix you up with it. If it is completely necessary for you I would recommend picking up some of our
Premium Support hours along with fill out a
Project Requirements form so we can get an estimate over to you for this functionality.
But Javascript would be the best way for you to do this.
Thanks,
Ryan