Private frmList As New List(Of Form2)
 
    Public Sub New()
        InitializeComponent()
        For i As Integer = 0 To 2
            frmList.Add(New Form2)
            frmList(i) = Nothing
        Next
    End Sub
 
    Private Sub ButtonAny_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click, Button2.Click, Button3.Click
        Dim i As Integer = CInt(CType(sender, Button).Name.Replace("Button", _
        "")) - 1
 
        If frmList(i) Is Nothing Then
            frmList(i) = New Form2
            frmList(i).ControlBox = False ' max/min/Schliessen entfernen
            frmList(i).TopMost = True
            frmList(i).Name = "frm" & i + 1
            frmList(i).Show()
            AddHandler frmList(i).FormClosed, AddressOf frmAny_FormClosed
        End If
    End Sub
 
    Private Sub frmAny_FormClosed(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.FormClosedEventArgs)
        frmList(CInt(CType(sender, Form2).Name.Replace("frm", "")) - 1) = _
        Nothing
    End Sub