Private p2Form As Form
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        setForm(New Form2)
    End Sub
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button2.Click
        setForm(New Form3)
    End Sub
 
    Private Sub setForm(ByVal f As Form)
        If p2Form IsNot Nothing Then
            p2Form.Dispose()
        End If
        p2Form = f
        p2Form.FormBorderStyle = Windows.Forms.FormBorderStyle.None
        p2Form.TopLevel = False
        p2Form.Dock = DockStyle.Fill
        p2Form.BackColor = Color.YellowGreen
        p2Form.Show()
        SplitContainer1.Panel2.Controls.Add(p2Form)
    End Sub