frm_00.Close()

    Private Sub VereinToolStripMenuItem_Click(sender As Object, e As EventArgs _
      Handles VereinToolStripMenuItem.Click
 
        ' Alte Form schließen
        If frm_00 IsNot Nothing Then frm_00.Close()
 
        frm_00 = New frm_Config_Club
        SetParent(frm_00.Handle, Me.spc_KassaBook.Panel2.Handle)
        frm_00.Location = New Point(0, 0)
        frm_00.Size = spc_KassaBook.Panel2.Size
        frm_00.Show()
    End Sub

Private m_LastForm As Form