TOPIC: insert data from another field as default?

I doubt this is possible, but is there a way I can pull data into a field from another field such as a CB field if a person is logged in?

There is auto-population of fields like name, address, city, phone, etc... but there is not a way presently to pull data into custom fields from CB.

probably a lot of work, but it'd be cool to have a dropdown of all fields that you could load automatically into a field. So, if I created a field called "nickname" then I could choose from a dropdown of all CB fields as to what would load into that field if someone were logged in. Just a dream request, I'm sure you're busy.