Hola otra vez.
No estoy seguro de haberte entendido bien, ni estoy seguro de no haberme liado mucho con el código

Pero, en fín Pilarín... Ahí va eso y tú veras si va bien la cosa:
Código HTML:
<html><head>
<script>
function sumar(num) {
elem=document.getElementById('ta').getElementsByTagName('tr')[num];
cel1=parseFloat(elem.getElementsByTagName('td')[1].childNodes[0].value);
cel2=parseFloat(elem.getElementsByTagName('td')[2].childNodes[0].value);
elem.getElementsByTagName('td')[3].childNodes[0].value=cel1 * cel2;
// Ahora vamos a sumar las columnas
var tot = new Array;
tot[1]=0; tot[2]=0; tot[3]=0;
for(i=1;i<4;i++) {
elem=document.getElementById('ta').getElementsByTagName('tr')[i];
for(j=1;j<4;j++)
tot[j]+=parseFloat(elem.getElementsByTagName('td')[j].childNodes[0].value);
}
for(i=1;i<4;i++)
document.getElementById(i).innerHTML=tot[i];
}
</script>
</head>
<body>
<form name="form" method="post" action="preview.fax.dedicated.php">
<table id="ta" width="600" border="0" align="center" cellpadding="0" cellspacing="2">
<tr>
<td align="center">Description of Service</td>
<td align="center">Quantity</td>
<td align="center">Unit Price </td>
<td align="center">Ext. Price </td>
</tr>
<tr align="center">
<td><input name="de_cs1" type="text" id="de_cs1" value="" size="60" maxlength="80"></td>
<td><input name="de_q11" type="text" id="de_q11" onkeyup="sumar(1)" value="0" size="6" maxlength="6"></td>
<td><input name="de_u11" type="text" id="de_u11" onkeyup="sumar(1)" value="0" size="6" maxlength="6"></td>
<td><input name="de_e11" type="text" id="de_e11" readonly="readonly" value="0" size="6" maxlength="6"></td>
</tr>
<tr align="center">
<td><input name="de_b1" type="text" id="de_b1" value="" size="60" maxlength="80"></td>
<td><input name="de_q12" type="text" id="de_q12" onkeyup="sumar(2)" value="0" size="6" maxlength="6"></td>
<td><input name="de_u12" type="text" id="de_u12" onkeyup="sumar(2)" value="0" size="6" maxlength="6"></td>
<td><input name="de_e12" type="text" id="de_e12" readonly="readonly" value="0" size="6" maxlength="6"></td>
</tr>
<tr align="center">
<td><input name="de_o1" type="text" id="de_o1" value="" size="60" maxlength="80"></td>
<td><input name="de_q13" type="text" id="de_q13" onkeyup="sumar(3)" value="0" size="6" maxlength="6"></td>
<td><input name="de_u13" type="text" id="de_u13" onkeyup="sumar(3)" value="0" size="6" maxlength="6"></td>
<td><input name="de_e13" type="text" id="de_e13" readonly="readonly" value="0" size="6" maxlength="6"></td>
</tr>
<tr align="center">
<td colspan="4"><strong>(Ext. Price = Unit Price * Quantity) </strong></td>
</tr>
<tr>
<td align="right">Total Setup fee* </td>
<td align="center" id="1">0</td>
<td align="center" id="2">0</td>
<td align="center" id="3">0</td>
</tr>
</table>
</form>
</body></html>
Saludos,