MSAccess Not In List Event
Simple VBA code for adding text typed into a combo box

Private Sub cmbTextToAdd_NotInList(NewData As String, Response As Integer)

 Dim db As DAO.Database
 Dim rs As DAO.Recordset

 If NewData = "" Then Exit Sub

 Set db = CurrentDb
 Set rs = db.OpenRecordset("tblTextToAdd", dbOpenDynaset)

 rs.AddNew
 rs![TextToAdd] = cmbTextToAdd
 rs.Update

 Response = acDataErrAdded

End Sub