Private lastIndex As Integer = -1
 
   Private Sub ComboBox1_KeyDown(ByVal sender As System.Object, ByVal e As _
     System.Windows.Forms.KeyEventArgs) Handles ComboBox1.KeyDown
      If e.KeyCode = Keys.Enter Then
         ComboBox1.Items(lastIndex) = ComboBox1.Text
      End If
   End Sub
 
   Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, _
     ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
      lastIndex = ComboBox1.SelectedIndex
   End Sub