Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e _
         As System.EventArgs) Handles TextBox1.TextChanged
        For i As Integer = 0 To ListBox1.Items.Count - 1
            Dim item As String = ListBox1.Items.Item(i).ToString
            If item.Length < TextBox1.TextLength Then
            Else
                item = item.Substring(0, TextBox1.TextLength)
            End If
            'prüfen ob textbox gleich einem item ist
            If TextBox1.Text = item Then
                ListBox1.SetSelected(i, True)
                Exit For
            End If
        Next
    End Sub

fg viperbone