Code:
    Dim rndm As New Random
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        If ListBox1.Items.Count > 0 Then
            Dim i As Integer = rndm.Next(0, ListBox1.Items.Count)
            TextBox1.Text = ListBox1.Items(i).ToString
            ListBox1.Items.RemoveAt(i)
        End If
    End Sub