ช่วยดูให้ที่ครับ การวนลูป คำนวนค่าออโต้ แล้วไม่ยอมคำนวณ

<table width="335" border="1" cellpadding="0" cellspacing="0">
<tr bgcolor="#9393FF">
  <td width="30">&nbsp;</td>
<td width="103" height="29">PART#</td>
    <td width="90">Qty</td>
    <td width="102">total cost</td>
    </tr>

<tbody id="datatable">
<?php $sql=("SELECT * FROM payment "); 
			$query=query_db($sql);
			while($row=fetch_db($query)){ 
?>

<tr>
  <td><INPUT type="checkbox" name="chk"/></td>
<td><input type="text"name="pro" value="<?php echo $row['before_price']; ?>"  size="7" onkeyup="checkvalue(this.value)"></td>
<td valign="top"><input type="text" name="data1[]" value="0" size="15" onkeyup="checkvalue(this.value)"></td>
        <td colspan="15" valign="top"><input type="text" name="todata2[]" size="10" onFocus="sumx()">          </td></td>
</tr>
</tbody>

<?php } ?>
</table>

$sql=("SELECT * FROM payment "); 
			$query=query_db($sql);
			$row=fetch_db($query)

<script language="JavaScript">
function sumx()
{
   //var pro = document.formx.pro.value;
   //var data1 = document.formx.data1.value;
   var pro = parseFloat(document.formx.pro.value);
	var data1 = document.getElementsByName("data1[]");
	var todata2 = document.getElementsByName('todata2[]');
	var total_cost = 0;
	var sum = 0;
	var count = data1.length;
	for(var a=0;a<count;a++){
		todata2[a].value = pro * data1[a].value;	
	}
   
   //document.formx.todata2.value = pro*data1
}
function addRow(){
var myTbody=document.getElementById('datatable');
newRow=myTbody.firstChild.cloneNode(true);
myTbody.appendChild(newRow);
}
function deleteRow(tableID) {  
           try {  
            var table = document.getElementById(tableID);  
            var rowCount = table.rows.length;  
             for(var i=0; i<rowCount; i++) {  
                 var row = table.rows[i];  
               var chkbox = row.cells[0].childNodes[0];  
              if(null != chkbox && true == chkbox.checked) {  
                  if(rowCount <= 1) {  
                         alert("Cannot delete all the rows.");  
                         break;  
                    }  
                     table.deleteRow(i);  
                   rowCount--;  
                    i--;  
                }  
            }  
            }catch(e) {  
                alert(e);  
            }  
        }  
</script>
<script language="JavaScript">
function check_number(ch){
	var len, digit;
	if(ch == " "){
		return false;
		len=0;
	}else{
		len = ch.length;
	}
	for(var i=0 ; i<len ; i++)
	{
			digit = ch.charAt(i)
		if(digit >="0" && digit <="9" || digit=="."){
			;
		}else{
			return false;
		}
	}
		return true;
	}


function checkvalue(val)
{
	if(!check_number(val))
	{
		alert('กรุณากรอกตัวเลข');
		return false;
	}else{	
		sumx();		
		return true;	
	}
}

</script>