private void PrepareInvoiceDocument(Worksheet worksheet, int itemsCount)
        {
            int lastItemIndexRow = IndexRowItemStart + itemsCount;

            CellIndex  firstUsedCellIndex = new CellIndex(0, 0);
            CellIndex  lastUsedCellIndex  = new CellIndex(lastItemIndexRow + 1, IndexColumnSubTotal);
            CellBorder border             = new CellBorder(CellBorderStyle.DashDot, InvoiceBackground);

            worksheet.Cells[firstUsedCellIndex, lastUsedCellIndex].SetBorders(new CellBorders(border, border, border, border, null, null, null, null));

            worksheet.Cells[firstUsedCellIndex].SetValue("INVOICE");
            worksheet.Cells[firstUsedCellIndex].SetFontSize(20);
            worksheet.Cells[firstUsedCellIndex].SetHorizontalAlignment(RadHorizontalAlignment.Center);
            worksheet.Cells[0, 0, 0, IndexColumnSubTotal].MergeAcross();

            worksheet.Columns[IndexColumnUnitPrice].SetWidth(new ColumnWidth(125, true));
            worksheet.Columns[IndexColumnSubTotal].SetWidth(new ColumnWidth(125, true));

            worksheet.Cells[IndexRowItemStart, 0].SetValue("Item");
            worksheet.Cells[IndexRowItemStart, IndexColumnQuantity].SetValue("QTY");
            worksheet.Cells[IndexRowItemStart, IndexColumnUnitPrice].SetValue("Unit Price");
            worksheet.Cells[IndexRowItemStart, IndexColumnSubTotal].SetValue("SubTotal");
            worksheet.Cells[IndexRowItemStart, 0, lastItemIndexRow, IndexColumnQuantity - 1].MergeAcross();

            worksheet.Cells[IndexRowItemStart, 0, IndexRowItemStart, IndexColumnSubTotal].SetFill
                (new GradientFill(GradientType.Horizontal, InvoiceBackground, InvoiceBackground));
            worksheet.Cells[IndexRowItemStart, 0, IndexRowItemStart, IndexColumnSubTotal].SetForeColor(InvoiceHeaderForeground);
            worksheet.Cells[IndexRowItemStart, IndexColumnUnitPrice, lastItemIndexRow, IndexColumnSubTotal].SetFormat(
                new CellValueFormat(AccountFormatString));

            worksheet.Cells[lastItemIndexRow + 1, 6].SetValue("TOTAL: ");
            worksheet.Cells[lastItemIndexRow + 1, 7].SetFormat(new CellValueFormat(AccountFormatString));

            string subTotalColumnCellRange = NameConverter.ConvertCellRangeToName(
                new CellIndex(IndexRowItemStart + 1, IndexColumnSubTotal),
                new CellIndex(lastItemIndexRow, IndexColumnSubTotal));

            worksheet.Cells[lastItemIndexRow + 1, IndexColumnSubTotal].SetValue(string.Format("=SUM({0})", subTotalColumnCellRange));

            worksheet.Cells[lastItemIndexRow + 1, IndexColumnUnitPrice, lastItemIndexRow + 1, IndexColumnSubTotal].SetFontSize(20);
        }