How to write a double value to an specified cell and worksheet in an excel file (C#)

Thanks to Vimal and and Sateesh, we could manage to read an excel file , and change one cell value to double(+doing some math operation).I want to write it back to excel by c#.

Would you please let me know how to :
1. write this new value(of type double) to another excel file(say Book.3) and in Worksheet3 and cell[12,1]

using System;

using System.Collections.Generic;

//using System.Linq;

using System.Text;

using System.Reflection;

using Microsoft.Office.Interop.Excel;

namespace ConsoleApplication1

{

class Program

{

static ApplicationClass App;

static Workbooks oBooks;

static Workbook oBook;

static Worksheet oSheet;

static void Main(string[] args)

{

App = null;

oBooks = null;

oBook = null;

oSheet = null;

Console.WriteLine("Enter the Excel file path");

string filepath = Console.ReadLine();

App = new ApplicationClass();

App.Visible = false;

oBooks = App.Workbooks;

//Open a new workbook

oBook = oBooks.Open(filepath,

Missing.Value,

Missing.Value);

oSheet = (Worksheet)App.ActiveSheet;

/* After that you can get your cells either by

* range */

Range myRange = oSheet.get_Range("A1", "C3");

//Or by cell

//oSheet.Cells.Cells[1, 1] = oSheet.Cells.Cells[1, 1] / 2;

for (int j = 1; j <= 2; j++)

{

for (int i = 1; i < 50; i++)

{

object m = ((Range)oSheet.Cells.Cells[i, j]).Text;

double x = Convert.ToDouble(m) / 2;

Console.WriteLine(x);

}

//You can get or create another sheet and transmit the content

if (App.Worksheets[2] != null)

{

Worksheet oSheet2 = App.Worksheets[2] as Worksheet;

oSheet2.Cells.Cells[1, 1] = oSheet.Cells.Cells[1, 1];

}

oBook.Save();

App.Quit();

System.Runtime.InteropServices.Marshal.ReleaseComObject(App);

App = null;

}