Linking fields on a form

[Ekly]

I'm making a form where a user can add people to a class. The fields on the form are CID (persons ID), First Name(person's first name), LastName (peron's last name), ClassName (name of the class), and Paid (amount they paid for the class). There's a button I put on the form that inserts the selected data into an enrollment table. The CID field is hidden to the user.

I have 2 questions:

1) I want to combine the FirstName and LastName fields together, so when you pull the drop down list it is displayed as "Last, First" and sorted ascending by last name. How do I do this?

2) How can I link the CID and name fields together so that when the name is selected, the CID field changes and displays the correct CID?

Thanks in advance; any help would be greatly appreciated.

Kyle