To send Email before 3 days from the Specified date using asp.net c#

private void OnElapsedTime(object source, ElapsedEventArgs e)
{
  TraceService("Another entry at "+DateTime.Now);
  ScheduleEmail();
}

protected override void OnStart(string[] args)
        {
            try
            {
                int iHourIn24HourFormat = Convert.ToInt32(DateTime.Now.ToString("HH"));
                int iCurrentMinutes = DateTime.Now.Minute;
                int iCurrentSecond = DateTime.Now.Second;

                int iFirstIntervalGapInHours = 24 - iHourIn24HourFormat;
                eventLog1.WriteEntry("Service Started ---->" + DateTime.Now.ToString());
                objTimer.Interval = (1000 * 60 * 60 * iFirstIntervalGapInHours) + (1000 * 60 * 60 * 2) - (1000 * 60 * iCurrentMinutes) - (1000 * iCurrentSecond); // at Every day 2:00 AM    
                eventLog1.WriteEntry("Interval -> " + objTimer.Interval.ToString());                

                objTimer.Enabled = true;
                objTimer.Elapsed += new ElapsedEventHandler(objTimer_Elapsed);
                objTimer.Start();
	}
            catch (Exception ex)
            {

                eventLog1.WriteEntry("Error: " + ex.Message);
            }            
        }

void objTimer_Elapsed(object sender, ElapsedEventArgs e)
        {
            try
            {
                eventLog1.WriteEntry("Timer Elapsed ---->" + DateTime.Now.ToString());

                objTimer.Interval = 1000 * 60 * 60 * 24; //set interval for every 1 day

                ContinueProcess();
            }
            catch (Exception ex)
            {
                eventLog1.WriteEntry("Error: " + ex.Message);
            }
        }


private void ContinueProcess()
        {
            HttpWebRequest objHttpWebRequest;
            HttpWebResponse objHttpWebResponse = null;
            try
            {
                objHttpWebRequest = (HttpWebRequest)WebRequest.Create("http://www.xyz.com/email_Service.aspx");
                objHttpWebRequest.Timeout = 300000;
                objHttpWebRequest.Proxy = null;
                objHttpWebRequest.Method = "Get";
                objHttpWebRequest.ContentLength = 0;
                objHttpWebResponse = (HttpWebResponse)objHttpWebRequest.GetResponse();
                Stream objResponseStream = objHttpWebResponse.GetResponseStream();                
            }
            catch (Exception ex)
            {
                eventLog1.WriteEntry("ContinueProcess Error: " + ex.Message);
            }
            finally
            {
                if (objHttpWebResponse != null)
                {
                    objHttpWebResponse.Close(); // Close web response Connection
                }
                objHttpWebRequest = null; //To clear up the web request
                objHttpWebResponse = null;//To clear up the web Response
            }
        }

protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
	//Add code to find the list of user to whom you wants to send email.
        }
   }