Confirming CB user name in a registration field

Is there a way for a user to type in a persons name in a field during registration and have CB scan our list of users to confirm that the person they type is a current user?

If so, is there a way to email that existing user when someone registers to say that the person registered and lists their registration details in an email?

Long story short, the registrant must use a reference (an existing customer) and that customer needs to see their registration details to confirm that they will refer that person.

Yes, using CB Query Field and its Query Validation on a text field. You'd create a query that queries the _users table and compares the value they supplied to the username column. As for emailing that user it maybe possible using CB Auto Actions and a second query field to grab the references email address, which you'd then substitute in for the To address of your email action that'd fire on the after registration trigger.

I don't know anything about CB Query Fields or Query Validation. Are there any tutorials on that?

Yes, see the below videos regarding CB Query Field.

www.youtube.com/playlist?list=PLp0puRITgC7MM9iP9FooKB1qk8f5MLWVp

The 2nd video was a little complicated for me but I think I get the basic idea.

Dumb question- where do I find my user table?

I just found out that the validation should be shown to the moderator only (not the registrant). We don't want the registrant to know if their field matches anyone in our database. But we do want the moderator to be able to see. Because if it's not a match, it could be spelling mistake etc. that only a live person will be able to confirm.

Is this possible or something custom I would have to pay you guys to set up?