[Marco van Herwaarden]

Well you could use a few approaches.

Consider adding a new table with the ID numbers (and maybe the matching mail address if you have them).

Now you could:
- Make a small script to pre-register them
- Or let all new registration to be admin moderated, and create a cron job that will scan all new registration once an hour, match the ID number, if ok --> registered, not OK-->delete
- Or Incorporate a test in the registration process so they can register if ID is not correct.

If you need help with this, you could PM me.