Private Sub Menu_Start_Form2_Click(ByVal sender As System.Object, ByVal e _
      As System.EventArgs) Handles Menu_Start_Form2.Click
        Dim  f2 As New Form2
        f2.MdiParent = Me
        f2.Show()
    End Sub

    Dim WithEvents f2 As Form2
 
    Private Sub Menu_Start_Form2_Click(ByVal sender As System.Object, ByVal e _
      As System.EventArgs) Handles Menu_Start_Form2.Click
        If Not f2 Is Nothing Then Return
        f2 = New Form2
        f2.MdiParent = Me
        f2.Show()
    End Sub
 
    Private Sub f2_Closed(ByVal sender As Object, ByVal e As System.EventArgs) _
      Handles f2.Closed
        f2 = Nothing
    End Sub