When using RadSpreadsheet how do I get filename that was loaded when user uses File Open?

        private void ActiveSheetEditor_UICommandExecuted(object sender, UICommandExecutedEventArgs e)
        {
            if (e.Command == this.radSpreadsheet1.SpreadsheetElement.CommandDescriptors.OpenFile.Command)
            {

            }
        }

        public RadForm1()
        {
            InitializeComponent();

            
            BackstageButtonItem myOpen = new BackstageButtonItem();
            myOpen.Click += MyOpen_Click;
            this.radSpreadsheetRibbonBar1.BackstageControl.Items.Insert(0, myOpen);
            myOpen.Image = ((BackstageButtonItem)this.radSpreadsheetRibbonBar1.BackstageControl.Items["backstageButtonOpen"]).Image;
          this.radSpreadsheetRibbonBar1.BackstageControl.Items["backstageButtonOpen"].Visibility = ElementVisibility.Collapsed;
        }

        private void MyOpen_Click(object sender, EventArgs e)
        {

            RadOpenFileDialog openFileDialog = new RadOpenFileDialog();
            DialogResult dr = openFileDialog.ShowDialog();
            if (dr == System.Windows.Forms.DialogResult.OK)
            {
                string fileName = openFileDialog.FileName;
                 
                var formatProvider = new XlsxFormatProvider();
                using (Stream input = new FileStream(fileName, FileMode.Open))
                {
                    radSpreadsheet1.Workbook = formatProvider.Import(input);
                }
            }
        }