Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim x As New Pen(Color.Aqua)

        passaggio(x)
    End Sub

    Private Function passaggio(Optional ByVal penna As Pen = Nothing)
        If penna Is Nothing Then
            MsgBox("Errore!")
            Return -1
        Else
            MsgBox("Evviva!")
            Return 1
        End If
    End Function