จะทำ Create Element ซ้อน Create Element ได้ไหมครับ

<table width="60%" border="0" align="center" cellpadding="3" cellspacing="3" id="tb_add">
<tr>
<th width="10%" align="left">Material No. #</th>
<th width="10%" align="left">Pro-Order No. #</th>
<th width="5%" align="left">&nbsp;</th>
</tr>
<tr>
<td width="10%" valign="middle"><input type='text' name='mat_no[]' class='wt mat_no' maxlength='8'/></td>
<td width="10%" valign="middle"><input type='text' name='prd_order[]' class='wt po_no' maxlength='8'/></td>
<td width="5%" valign="middle"><input type="button" name="button" id="button" value="+ เพิ่มแถว" class="add btn"/></td>
</tr>
</table>

<script type="text/javascript">
$(function(){
$('.add').live('click',function(){
		$(this).val('- ลบแถว');
		$(this).attr('class','del btn');
		var appendTxt = "<tr><td width='10%' valign='middle'><input type='text' name='mat_no[]' class='wt mat_no' maxlength='8'/></td><td width='10%' valign='middle'><input type='text' name='prd_order[]' class='wt po_no' maxlength='8'/></td><td valign='middle'><input type='button' name='button' id='button' value='+ เพิ่มแถว' class='add btn'/></td></tr>";
		$("#tb_add").append(appendTxt);			
	});
});
</script>