Enrolment

We sell continuing education courses. We have both individuals and companies buy our courses. If a company buys the course for multiple users I am assuming we need to use a course key code that can be distributed to the students, but we need to limit the use by that company by the number of incidents of the course they buy.

How would we do this? and if we use Course key codes, can moodle recognize different codes for the same course?

I have done some reading about manual registration, can this be accomplished by a fill in form and xml?

Thanks for any guidance you can provide