Hi, what would be the best way to prompt a user, take the answer to then use is in a bundle?

I am looking to build a way to promote a user to the administrator group, my approche is to build an app that you can enter a temp key that would by given to the user that call's in to the office, a support tech would generate a key and tell the user so that when the user enters the temp key the would become part of the admin group that is simple, passing the value on to the next process in line within a bundle is what I am looking for.

Thanks to any who can help!