Dynamic textboes generating three times

protected void TextBox2_TextChanged(object sender, EventArgs e)
{
   foreach (GridViewRow i in GridView1.Rows) 
   {
      CheckBox chkUpdate = (CheckBox)i.Cells[0].FindControl("CheckBox1");
      if (chkUpdate != null)
      {
         if (chkUpdate.Checked == true)
         {
            Label lab = (Label)i.FindControl("Label1");
            TextBox txt = (TextBox)i.FindControl("TextBox2");
            PlaceHolder ph = (PlaceHolder)i.FindControl("PlaceHolder1");
            if (txt.Text != "")
            {
               for (int j = 0; j < Convert.ToInt16(txt.Text); j++)
               {
                  Label la1 = new Label();
                  la1.Text = lab.Text + (j + 1).ToString();
                  //  la1.ID = "abc" + j;
                  using (SqlCommand comm = new SqlCommand("select [Serial_Number_Required] from Products where Product=@Product ", con))
                  {
                     con.Open();
                     //string Role = (string)(Session["Role"]);
                     // 2. define parameters used in command object
                     SqlParameter para = null;
                     para = new SqlParameter();
                     para.ParameterName = "@Product";
                     para.Value = lab.Text;
                     comm.Parameters.Add(para);

                     //Pass @Pages parameter

                     SqlDataReader reade = comm.ExecuteReader();
                     while (reade.Read())
                     {
                        Session["Serial_Number_Required"] = Convert.ToString(reade["Serial_Number_Required"]);
                     }

                     con.Close();
                     //Button Add = (Button)PreviousPage.FindControl("Button2");
                     if (Session["Serial_Number_Required"].ToString() == "Y")
                     {
                        ph.Controls.Add(la1);
                        ph.Controls.Add(new LiteralControl("<input id='txt' name='Textbox" + j + "'type='Text'  />"));

                        ph.Controls.Add(new LiteralControl("<br/>"));
                     }
                  }
               }
            }
         }
      }
   }
}