не хочу.

Тогда вот:

<script type="text/javascript">
function evalSize() {
  var dFiles = document.getElementById('dgFiles');
  var size = 0;
  
  for (i = 0; i < dFiles.rows.length; i++) 
			size += parseFloat(dFiles.rows[i].cells[0].innerText);
  
  document.getElementById('result').innerHTML = size;
  totalSize.style.display = "";
}

</script>

<div>Total size: <span id="result"><button onclick="evalSize()">calculate</button></span></div>
<table id="dgFiles">
<tr>
	<td>1</td>
</tr>
<tr>
	<td>7</td>
</tr>
<tr>
	<td>2</td>
</tr>
<tr>
	<td>4</td>
</tr>
</table>

Выводы делай сам