Public Class Form1
    '// Designer
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        Me.ListBox1.DisplayMember = "DisplayValue"
        Me.ListBox1.ValueMember = "Value"
        Me.ListBox1.Items.Add(New Eintrag("Test1", "Anzeige1"))
        Me.ListBox1.Items.Add(New Eintrag("Anzeige2"))
 
    End Sub
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button2.Click
        Dim item As Eintrag = CType(Me.ListBox1.Items(0), Eintrag)
        item.DisplayValue = "hello world"
        Me.ListBox1.Items(0) = item
    End Sub
End Class

Public Class Form1
    '// Designer
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        Me.ListBox1.Items.Add(New Eintrag("Test1", "Anzeige1"))
        Me.ListBox1.Items.Add(New Eintrag("Anzeige2"))
    End Sub
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button2.Click
        Dim item As Eintrag = CType(Me.ListBox1.Items(0), Eintrag)
        item.DisplayValue = "hello world"
        Me.ListBox1.Items(0) = item
    End Sub
End Class
 
Public Class Eintrag
 
    [...]

    Public Overrides Function ToString() As String
        Return Me.DisplayValue
    End Function

End Class