Управление ячейками в MS Excel

Microsoft.Office.Interop.Excel.Application ObjExcel = new Microsoft.Office.Interop.Excel.Application();
            Microsoft.Office.Interop.Excel.Workbook ObjWorkBook;
            Microsoft.Office.Interop.Excel.Worksheet ObjWorkSheet;
           
            ObjWorkBook = ObjExcel.Workbooks.Open(saveFileDialog1.FileName,
            Type.Missing, Type.Missing, Type.Missing, Type.Missing,
            Type.Missing, Type.Missing, Type.Missing, Type.Missing,
            Type.Missing, Type.Missing, Type.Missing, Type.Missing,
            Type.Missing, Type.Missing);
            
            ObjWorkSheet = (Microsoft.Office.Interop.Excel.Worksheet)ObjWorkBook.Sheets[1];
 
            ObjWorkSheet.Cells[2, 2] = "Hi!";
//тут нужно менять стиль ячейки
            
            ObjExcel.Visible = true;
            ObjExcel.UserControl = true;

using System;
using Excel = Microsoft.Office.Interop.Excel;
 
class Program
{
    static void Main(string[] args)
    {
        Excel.Application application = new Excel.Application();
        Object missing = Type.Missing;
        //добавили книгу
        application.Workbooks.Add(missing);
        Excel.Worksheet sheet = (Excel.Worksheet)application.ActiveSheet;
        //вписываем текст
        sheet.Cells[1, 1] = "hi!";
        ((Excel.Range)sheet.Columns).ColumnWidth = 15;
        //жирность
        (sheet.Cells[1, 1] as Excel.Range).Font.Bold = true;
        //размер шрифта
        (sheet.Cells[1, 1] as Excel.Range).Font.Size = 16;
        //название шрифта
        (sheet.Cells[1, 1] as Excel.Range).Font.Name = "Times New Roman";
        //стиль границы
        (sheet.Cells[1, 1] as Excel.Range).Borders[Excel.XlBordersIndex.xlEdgeBottom].LineStyle = Excel.XlLineStyle.xlDouble;
        //толщина границы
        (sheet.Cells[1, 1] as Excel.Range).Borders[Excel.XlBordersIndex.xlEdgeBottom].Weight = Excel.XlBorderWeight.xlMedium;
        //выравнивание по горизонтали
        (sheet.Cells[1, 1] as Excel.Range).HorizontalAlignment = Excel.XlHAlign.xlHAlignCenter;
        //выравнивание по вертикали
        (sheet.Cells[1, 1] as Excel.Range).VerticalAlignment = Excel.XlVAlign.xlVAlignCenter;
        //объединение ячеек
        sheet.get_Range(sheet.Cells[2, 2], sheet.Cells[4, 4]).Merge(missing);
        application.Visible = true;
    }
}

sheet.get_Range(sheet.Cells[2, 2], sheet.Cells[4, 4]).Merge(missing);

sheet.get_Range(sheet.Cells[2, 2], sheet.Cells[4, 4]).Merge(missing);

Excel.Range oRange;
 
            oRange = ObjWorkSheet.Range[ObjWorkSheet.Cells[4, 2], ObjWorkSheet.Cells[4, human + 4]];
            oRange.Merge(Type.Missing);