Sub t_84()
    Dim objC As Range
        For Each objC In Range("a2:a23")
            objC.FormulaLocal = "=ГИПЕРССЫЛКА(""" & objC.Value & """)"
        Next
End Sub

    class Program
    {
        static string attfile = @"C:\Excel_temp\ext\Новички_без_звонков.xlsx";
        static Excel.Application excelApp = new Excel.Application();
        static Excel.Workbook excelBook;
        static int rowcount;
        static string reportingdate;


        static void Main()
        {
            exceling();
            if (rowcount > 1)
            {
                mailing();
            }        
        }

        public void t_84()
        {
            Range objC = default(Range);
            foreach ( objC in Range("a2:a23")) 
            {
                objC.FormulaLocal = "=ГИПЕРССЫЛКА(\"" + objC.Value + "\")";
            }
        }

        public static int LastRowCell()
        {
            int lastrow = excelApp.Sheets[1].Cells.SpecialCells(Excel.XlCellType.xlCellTypeLastCell).Row;
            for (int i = lastrow; i >= 1; i--)
            {
                if (excelApp.Cells[i, 2].Value != null)
                {
                    rowcount = i;
                    break;
                }
            }

            return rowcount;
        }

        static void exceling()
        {
            excelApp.Visible = false;
            excelBook = excelApp.Workbooks.Open(attfile);

            foreach (Excel.WorkbookConnection cnn in excelBook.Connections)
            {
                cnn.OLEDBConnection.BackgroundQuery = false;
            }

            excelBook.RefreshAll();
            LastRowCell();
            excelBook.Save();
            excelBook.Close(0);
            excelApp.Quit();

        }