Module modul1  
Sub point(ByVal x%, ByVal y%, Optional ByVal pen As System.Drawing.Pen = _
  Pens.Blue)
        ...DrawEllipse(...pen,..x,y,..
   End Sub
end Module

Public Class Class1
    Public Sub point(ByVal x As Integer, ByVal y As Integer, Optional ByVal pen _
      As System.Drawing.Pen = Nothing)
        Dim penVal As Pen = pen
        If penVal Is Nothing Then penVal = Pens.Blue
        '...
    End Sub
End Class

Sub PicBox()
        Dim P As New PictureBox
        With P
            .Visible = True
            .Dock = DockStyle.Fill
            .BackColor = Color.Black
        End With
        Form1.Controls.Add(P)

Sub PicBox(ByVal frm As Form)
        Dim P As New PictureBox
        With P
            .Visible = True
            .Dock = DockStyle.Fill
            .BackColor = Color.Black
        End With
        frm.Controls.Add(P)
        frm.Refresh
End Sub