Public Class Form1
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
        Me.IsMdiContainer = True
        Dim form_navi As Form = New Form2
        form_navi.MdiParent = Me
        form_navi.Show()
    End Sub
End Class
 
 
Imports System.Threading
Public Class Form2
    WithEvents Button1 As New Button
    Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
        Button1.Text = "Neu"
        Me.Controls.Add(Button1)
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        Dim form_load As Form = New Form
        form_load.MdiParent = Form1
        form_load.Show()
        Thread.Sleep(1000)
        form_load.SendToBack()
    End Sub
End Class