[Deff]

<div  id=sum>
  <span><!--></span
</div>

<script type="text/javascript">

   $("#add").click(function () {
   var TR_add='<tr id="'+id+'"><td></td></tr>';
   var INPadd='<input type="button" id="delete" value="Удалить" del="'+id+'" />';
   var attachadd='\
<td>'+par1+'</td>\
<td>'+par2+'</td>\
<td>'+par3+'</td>\
<td>'+par4+'</td>\
<td>'+par5+'</td>\
<td>'+par6+'</td>\
<td id="potoktd">\'+par7+'</td>\
<td id="archivetd">'+par8.toFixed(0)+'</td>\
<td>'+INPadd+'</td>'

   $("#tableName").append(TR_add);  
   $('#'+id+':first').html(attachadd);
   id++; sum = 0;

   for (var j=1; j<id; j++) {
     sum += parseFloat($("table#tableName tr:eq("+j+") td:eq(6)").html()); 
   };
   alert(sum);
   $("div #sum span").text(sum);

  });
</script>