Screw Driver

Hello, I am looking to add a mechanism to my cnc project to put screws in a
whole.
I recently purchesed a screw feeder (
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2593462914&category=31483&sspagename=STRK%3AMEBWN%3AIT&rd=1 )

and I was thinking of using an extra stepper motor to place screws in a pre
existing 3/16 hole. This will have to all be done automatic (via software
programming and the right hardware)...
oh yeah, also the kicker is, if there is already a screw in the hole, it
must remove it until the hole is ready to be closed again with the screw.

Any suggestions past.. using a magnetic phillips head, would be much
appreciated :)

thanks-Lee