Declare Auto Function SetParent Lib "user32" (ByVal hWndChild As IntPtr, _
      ByVal nWndPArent As IntPtr) As Integer
    Private Property frm_00 As frm_Config_Club
    Private Sub VereinToolStripMenuItem_Click(sender As Object, e As EventArgs _
      Handles VereinToolStripMenuItem.Click
        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

For each Form in Panel2
       Form.close
next