Update cell value

Hi,
I want to put text into one cell, while I know Cell reference is like B2. How to adjust this

 public static void InsertText(string docName, string text)
{
    // Open the document for editing.
    using (SpreadsheetDocument spreadSheet = SpreadsheetDocument.Open(docName, true))
    {
        // Get the SharedStringTablePart. If it does not exist, create a new one.
        SharedStringTablePart shareStringPart;
        if (spreadSheet.WorkbookPart.GetPartsOfType<SharedStringTablePart>().Count() > 0)
        {
            shareStringPart = spreadSheet.WorkbookPart.GetPartsOfType<SharedStringTablePart>().First();
        }
        else
        {
            shareStringPart = spreadSheet.WorkbookPart.AddNewPart<SharedStringTablePart>();
        }

        // Insert the text into the SharedStringTablePart.
        int index = InsertSharedStringItem(text, shareStringPart);

        // Insert a new worksheet.
        WorksheetPart worksheetPart = InsertWorksheet(spreadSheet.WorkbookPart);

        // Insert cell A1 into the new worksheet.
        Cell cell = InsertCellInWorksheet("A", 1, worksheetPart);

        // Set the value of cell A1.
        cell.CellValue = new CellValue(index.ToString());
        cell.DataType = new EnumValue<CellValues>(CellValues.SharedString);

        // Save the new worksheet.
        worksheetPart.Worksheet.Save();
    }
}

that is from this URL, to update specific cell to given value?

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Many Thanks & Best Regards, Hua Min