Private Sub Form_Load()
    List1.AddItem "Test 1"
    List1.AddItem "Test 2"
    List1.AddItem "Test 3"
    List1.AddItem "Test 4"
    List1.AddItem "Test 5"
End Sub
 
Private Sub List1_ItemCheck(Item As Integer)
    If List1.Selected(Item) Then
        List2.AddItem List1.Text
    Else
        While Not List1.Text = List2.Text And _
              Not List2.ListIndex > List2.ListCount
              List2.ListIndex = List2.ListIndex + 1
        Wend
        List2.RemoveItem List2.ListIndex
    End If
 
End Sub