Public Sub New()
  InitializeComponent()

  ListBox1.Items.Add("An item")
  ListBox1.Items.Add("Another item")
  ListBox1.Items.Add("This is an item too")
  ListBox1.Items.Add("This item is initially selected")
  ListBox1.Items.Add("Yet another item")

  ListBox1.Sorted = True
  ListBox2.Sorted = True
End Sub

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
  MoveItem(ListBox1, ListBox2)
End Sub

Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
  MoveItem(ListBox2, ListBox1)
End Sub

Private Sub MoveItem(fromBox As ListBox, toBox As ListBox)
  If fromBox.SelectedIndex > ListBox.NoMatches Then
    Dim moveText As String = fromBox.Items(fromBox.SelectedIndex)
    fromBox.Items.RemoveAt(fromBox.SelectedIndex)

    toBox.Items.Add(moveText)
    toBox.SelectedIndex = toBox.Items.IndexOf(moveText)
  End If
End Sub