Dim sfd As New SaveFileDialog
        Dim res As DialogResult
        Dim b As Boolean = False
        sfd.InitialDirectory = "D:\"
        sfd.FileName = "foo.txt"
        Do
            res = sfd.ShowDialog()
            b = (IO.Path.GetFileName(sfd.FileName) = "foo.txt" AndAlso res = _
              Windows.Forms.DialogResult.OK) _
                    OrElse (res = Windows.Forms.DialogResult.Cancel)
            If Not (b) Then
                MessageBox.Show("Falscher Dateiname!")
            End If
        Loop While Not (b)