var c_delta = 5; //constant

function add_instruments(table_id, curr_no, new_no)
{
  var l_table = document.getElementById(table_id);
  var l_old_row = l_table.rows[1]; //the first one is header
  var l_old_select = l_old_row.cells[0].childNodes[0];
  var l_old_input = l_old_row.cells[1].childNodes[0];
  for (l_new_no = curr_no + 1; l_new_no <= curr_no + new_no; l_new_no++)
  {
    var l_new_row = l_table.insertRow(l_new_no);
    var l_td1 = document.createElement("td");
    var l_select = l_old_select.cloneNode(true);
    //document.write(l_old_select.nodeValue);
    l_select.value = "instrument_arr[" + l_new_no + "]";
    l_select.size = 1;
    l_td1.appendChild(l_select);
    var l_td2 = document.createElement("td"); 
    var l_input = l_old_input.cloneNode(true);
    l_input.name = "instr_count[" + l_new_no + "]";
    l_input.value = "";
    l_td2.appendChild(l_input);
    l_new_row.appendChild(l_td1);
    l_new_row.appendChild(l_td2);
  }
}