' BEI frm_PublicSection
 Private _Form As Form
    Public Shadows Sub Show(ByVal _Form As Form)
        MyBase.Show()
        Me._Form = _Form
    End Sub
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        Me._Form.Visible = Not _Form.Visible ' hier kannst du die Eigenschaft 
        ' ändern
    End Sub

' BEI frm_certify
        Dim f As New Form2
        Me.Visible = Not Me.Visible
        f.Show(Me)