Script for joining WPA2 Personal Wireless Network

Ok Guys, Been working on this a while and getting nowhere. I have read all of the previous posts I could find, but most of them had to do with 802.1x. We are about to switch our open wireless network to WPA2 Personal. What I am trying to do is push a file or script out to my clients while they are still connected to our open network so that when we change it, they already have the new secure network in their preferred networks and it just joins up. I do not want my end users to have the password. I would also like to be able to run this in my imaging process as a first boot script and probably for all my student machines have it run at every boot so that if for any reason a student gets where he or she can't join, all they have to do is reboot to connect back up. A special thanks to Spider for all of his help already on Launch Daemons and first boot scripts! Thanks, Mitchell