int rowCount = importxls.ActiveWorksheet.UsedCellRange.RowCount;
                int lastcolumn = importxls.ActiveWorksheet.UsedCellRange.ColumnCount;

                MessageBoxResult result = MessageBox.Show(rowCount.ToString());

                // Create a new checkbox and set its properties
                CheckBox checkbox = new CheckBox();
                checkbox.IsChecked = true;
                checkbox.VerticalAlignment = VerticalAlignment.Center;
                checkbox.Margin = new Thickness(5, 0, 0, 0);

                DependencyProperty chkBox = DependencyProperty.Register(
                      "Select", typeof(bool), typeof(CheckBox),
                      new UIPropertyMetadata(checkbox.IsChecked));

                for (int rowIndex = 0; rowIndex < rowCount; rowIndex++)
                {
                    
                    // Add the checkbox to the current row
                    RowSelection rowSelection = importxls.ActiveWorksheet.Rows[rowIndex];
                    CellIndex cellIndex = new CellIndex(rowIndex, lastcolumn);
                    CellSelection cellSelection = rowSelection.Worksheet.Cells[cellIndex];

                    cellSelection.SetValue(DateTime.Now); //checkbox should be here

                }