datagridView1.Rows.Add to a log file

I found what I did bad.
Instead to Create the text file i had to do Append

I found Out how to log the info to the log file.But now I have another problem and it is that I have a loop and only the last one will be send to the log file.
Here is my code:

 for (m = 0; m < listBox1.Items.Count; m++)
            {
                if (m == 0)
                {
                    dataGridView1.Rows.Clear();
                }


               for (count = 1; count <= n; count++)
                {
                  //  int b = 0;
                 //   TimeSpan ts = new TimeSpan(0, 0, 0, a);
                  //  int days = ts.Days;
                 //   int hours = ts.Hours;
                 //   int mins = ts.Minutes;
                  //  int sec = ts.Seconds;

                    FileStream f = new FileStream("output.txt", FileMode.Create);
                    StreamWriter s = new StreamWriter(f);
                            
                           dataGridView1.Rows.Add(listBox1.Items[m].ToString(),      
                           count,+ ts.Days+"d"+ts.Hours+"h"+ts.Minutes+"M"+ts.Seconds+"sec", count * a * a, DateTime.Now.ToString());
                      
                           s.Write(listBox1.Items[m].ToString());
                           s.Write(",");
                           s.Write(count);
                           s.Write(",");
                           s.Write(ts.Days + "Days " + ts.Hours + "Hrs " + ts.Minutes +  "Min " + ts.Seconds + "Sec");
                           s.Write(",");
                           s.Write(count * a*a);
                           s.Write(",");
                           s.Write(DateTime.Now.ToString());
                           s.Close();
                           f.Close();
                   a++;
                    }
           }

This Code is in mine timer_Tick Method