ผมอยากจะรวมค่าใน textbox ในคอลั่มสุดท้ายทั้งหมดต้องทำยังไงครับ

<meta charset="utf-8">
<script type="text/javascript">

function add_report_row()
{
var container   = document.getElementById('inputboxes_description');
var blank                       = document.createTextNode(" ");
var br_                         = document.createElement("br");
var report_row  = document.createElement("div");
var delete_link = document.createElement("a");
var nums                        = parseInt(document.getElementById('nums').value)+1;
document.getElementById('nums').value = nums;
var rowId = 'row'+nums;
var descName = "desc["+nums+"]";
var widName = "wid["+nums+"]";
var highName = "high["+nums+"]";
var totalName = "total["+nums+"]";
function textarea_add(id_,cols_)
                {
                        var textArea            = document.createElement("textarea");
                        textArea.setAttribute('id',id_);
                        textArea.setAttribute('names',id_);
                        textArea.setAttribute('cols',cols_);
                        return textArea;
                }

report_row.setAttribute('id',rowId);
report_row.appendChild(textarea_add(descName,'25'));
report_row.appendChild(blank);
report_row.appendChild(textarea_add(widName,'15'));
report_row.appendChild(blank);
report_row.appendChild(textarea_add(highName,'15'));
report_row.appendChild(blank);
report_row.appendChild(textarea_add(totalName,'15'));
report_row.appendChild(blank);


delete_link.setAttribute("href","javascript:;");
delete_link.onclick = function()        {del_report_row(rowId);}
delete_link.innerHTML = '[ลบ]';
report_row.appendChild(delete_link);            

report_row.appendChild(br_);
container.appendChild(report_row);
document.getElementById(widName).onkeyup = function () 
        {
                document.getElementById(totalName).value = document.getElementById(widName).value *1 * document.getElementById(highName).value  * 1;
				if( document.getElementById(totalName).value=="NaN"){ document.getElementById(totalName).value = "0";}
        }
document.getElementById(highName).onkeyup= function () 
        {
                document.getElementById(totalName).value = document.getElementById(widName).value *1 * document.getElementById(highName).value  * 1;
				if( document.getElementById(totalName).value=="NaN"){ document.getElementById(totalName).value = "0";}
        }
}
/*function fncCal()
{
var sum = 0;
for(var i = 0; i<totalName.length; i++){        
		if (totalName[i] instanceof Array) { sum += fncCal(totalName[i]);}
     if (totalName[i] === Math.round(totalName[i])) {sum += totalName[i];}
		}
		return sum;
}*/
function del_report_row(rows)
{
                        var container = document.getElementById('inputboxes_description');
                        if (confirm('delete rows?'))
                                {
                                        container.removeChild(document.getElementById(rows));
                                }
}
</script> 

<form name="formx">
<input id="nums" type="hidden" value="0" />
<table width="780" border="1" align="center" cellpadding="0" cellspacing="0" bordercolor="#e4dabf" class="bold1">
        <tr align="center" valign="middle" class="bold1">
                <td width="211" bgcolor="#e4dabf">Object</td>
                <td width="155" bgcolor="#e4dabf">Width</td>
                <td width="150" bgcolor="#e4dabf">Height</td>
                <td width="150" bgcolor="#e4dabf">Total</td>
        </tr>
        <tr align="center">
                <td  height="30" colspan="4" align="center" valign="top">
                <div id="inputboxes_description"> 
                </div>
                <br/>
               <button onclick="add_report_row();return false;"/>เพิ่มวัสดุ</button>
				Total :<input type="text" name="totalcal" id="totalcal" value="" onfocus="fncCal();">

				</td>
        </tr>
</table>
</form> 
<script language="javascript">
<?php foreach(array(1,2,3,4,5) as $n): ?>
         add_report_row();
<?php endforeach; ?> 
 </script>