How to write into the eventlog custom journal with impersonalization in code

private const string LOG_NAME = "MSCRM.Common";

/// 

/// Write message in log
/// 
public static void WriteLog(string message, Exception exception)
{
      System.Security.Principal.WindowsImpersonationContext ctx = null;
      ctx = System.Security.Principal.WindowsIdentity.Impersonate(IntPtr.Zero);
      try
      {
        string logSource = "MSCRM.Common.Web.Controls.Grid";

        if (EventLog.SourceExists(logSource))
        {
          if (!EventLog.LogNameFromSourceName(logSource, ".").Equals(LOG_NAME))
          {
            EventLog.DeleteEventSource(logSource, ".");
            EventLog.CreateEventSource(logSource, LOG_NAME);
          }
        }
        else 
        {
          EventLog.CreateEventSource(logSource, LOG_NAME);
        }
        EventLog el = new EventLog();
        el.Log = LOG_NAME;
        el.Source = logSource;
        el.WriteEntry(String.Format("{0}\nDetails:\n{1}", message, GetLogInfo(exception)), EventLogEntryType.Error);
      }
      catch (Exception ex)
      {
        throw ex;
      }
      finally
      {
        ctx.Undo();
      }
}