Public Class Form1
 
    Dim myChild As New Form2
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
        Me.IsMdiContainer = True
        myChild.MdiParent = Me
    End Sub
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        myChild.Show()
    End Sub
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button2.Click
        myChild.Hide()
    End Sub
End Class

  Private Sub Form2_FormClosing(ByVal sender As Object, ByVal e As _
    System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        If e.CloseReason = CloseReason.MdiFormClosing Then
            e.Cancel = True
            Me.Hide()
        End If      
    End Sub

Mein.Status = Status.WarteAufWeitereFragen