Private Function chkFile(ByVal path As String) As String
        If System.IO.File.Exists(path) Then
            Try
                Dim fs As New System.IO.FileStream(path, IO.FileMode.Open, IO.FileAccess.ReadWrite, IO.FileShare.None)
                fs.Close()
                Return "ok"
            Catch ex As Exception
                Return "in uso"
            End Try
        Else
            Return "non esiste"
        End If
    End Function