using (SpreadsheetDocument spreadSheet = SpreadsheetDocument.Open(ms, false))
{
   WorksheetPart wSheet = SpreadsheetReader.GetWorksheetPartByName(spreadSheet, "NameSheet");
   Cell cell =  WorksheetReader.GetCell("D", 2, wSheet);
}

public static Cell GetCell(string columnName, uint rowIndex, WorksheetPart worksheetPart)
        {
            Worksheet worksheet = worksheetPart.Worksheet;
            SheetData sheetData = worksheet.GetFirstChild<SheetData>();
            string cellReference = (columnName + rowIndex.ToString());

            // If the worksheet does not contain a row with the specified row index, insert one.
            Row row;
            if (sheetData.Elements<Row>().Where(r => r.RowIndex.Value == rowIndex).Count() != 0)
            {
                row = sheetData.Elements<Row>().Where(r => r.RowIndex.Value == rowIndex).First();
            }
            else
            {
                return null;
            }

            //If there is not a cell with the specified column name, return null 
            IEnumerable<Cell> cells = row.Elements<Cell>().Where(c => c.CellReference.Value == cellReference);
            if (cells.Count() > 0)
            {
                return cells.First();
            }
            else
            {
                return null;
            }
        }

private static string ExcelSerialDateToDMY(int nSerialDate)
{
    // Excel/Lotus 123 have a problem with 29-02-1900. 1900 is not a leap year, but Excel/Lotus 123 think it is...

    int nDay;
    int nMonth;
    int nYear;

    if (nSerialDate == 60)
    {
        nDay = 29;
        nMonth = 2;
        nYear = 1900;

        return nDay + "-" + nMonth + "-" + nYear;
    }

    if (nSerialDate < 60)
    {
        // Because of the 29-02-1900 problem, any serial date under 60 is one off... Compensate.
        nSerialDate++;
    }

    // Modified Julian to DMY calculation with an addition of 2415019
    var l = nSerialDate + 68569 + 2415019;
    var n = (4 * l) / 146097;
    l = l - (146097 * n + 3) / 4;
    var i = (4000 * (l + 1)) / 1461001;
    l = l - (1461 * i) / 4 + 31;
    var j = (80 * l) / 2447;
    nDay = l - (2447 * j) / 80;
    l = j / 11;
    nMonth = j + 2 - (12 * l);
    nYear = 100 * (n - 49) + i + l;

    return nDay + "-" + nMonth + "-" + nYear;
}