Try this basic DOM example. You may add as many rows/columns with text fields you want. No need to modify script or give id or names to your text fields, but if you need extra cells in table (with no textfield in them) take care about the arrays increment.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Untitled Document</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta http-equiv="Content-Style-Type" content="text/css">
<meta http-equiv="Content-Script-Type" content="text/javascript">
<script language="JavaScript" type="text/JavaScript">
function calculate(c){
d=document.getElementById('tab');
totRow=0;
totCol=0;
for(var i=0;i<d.rows.length;i++){
for(var j=0;j<d.rows[i].cells.length;j++){
if(c.parentNode==d.rows[i].cells[j]){
for (var k=0;k<d.rows[i].cells.length-1;k++){
totRow=totRow+Number(d.rows[i].cells[k].firstChild.value);
}
for (var m=0; m<d.rows.length-1;m++){
totCol=totCol+Number(d.rows[m].cells[j].firstChild.value);
}
d.rows[i].cells[d.rows[i].cells.length-1].firstChild.nodeValue=totRow;
d.rows[d.rows.length-1].cells[j].firstChild.nodeValue=totCol;
}
}
}
}
</script>
</head>
<body>
<form>
<table width="400" border="0" cellpadding="4" id="tab">
<tr>
<td><input type="text" onkeyup="calculate(this)"></td>
<td><input type="text" onkeyup="calculate(this)"></td>
<td width="10%" bgcolor="#CCCCCC"> </td>
</tr>
<tr>
<td><input type="text" onkeyup="calculate(this)"></td>
<td><input type="text" onkeyup="calculate(this)"></td>
<td bgcolor="#CCCCCC"> </td>
</tr>
<tr>
<td><input type="text" onkeyup="calculate(this)"></td>
<td><input type="text" onkeyup="calculate(this)"></td>
<td bgcolor="#CCCCCC"> </td>
</tr>
<tr bgcolor="#CCCCCC">
<td> </td>
<td> </td>
<td> </td>
</tr>
</table>
</form>
</body>
</html>