Hi,
I had need for this type of thing several years ago. My client sold drugs. Some of them could only be sold to doctors who could write prescriptions. We needed a way to mark customers as prescription capable so the drugs would only be sold to those doctors. I couldn't find anything out there at the time. We ended up writing a little add-in that would check the customer's status when one of the prescription-required items were selected. It was not a very elegant solution, but it worked well enough. Still, it was easy to overcome if you really wanted to.
I'm hoping someone has created one by now.
Kind regards,
Leslie