I would suggest that you switch over to a UserForm rather than use
formfields in a protected document.

See the article "How to create a Userform" at:

http://word.mvps.org/FAQs/Userforms/CreateAUserForm.htm

And, here's how you would populate a listbox (or a combobox with data from a
table in a database (Access)

Private Sub UserForm_Initialize()

   Dim db As DAO.Database

   Dim rs As DAO.Recordset

   Dim NoOfRecords As Long

   ' Open the database

   Set db = OpenDatabase("D:\Access\ResidencesXP.mdb")

   ' Retrieve the recordset

   Set rs = db.OpenRecordset("SELECT * FROM Owners")

   ' Determine the number of retrieved records

   With rs

        .MoveLast

        NoOfRecords = .RecordCount

        .MoveFirst

   End With

   ' Set the number of Columns = number of Fields in recordset

   ListBox1.ColumnCount = rs.Fields.Count

   ' Load the ListBox with the retrieved records

   ListBox1.Column = rs.GetRows(NoOfRecords)

   ' Cleanup

   rs.Close

   db.Close

   Set rs = Nothing

   Set db = Nothing

End Sub