Sum values

webmark

Here http://webmark.pt/sharepics/orders.png is the sales order layout (./sharepics/add.zip the full code) that I need to customize.

Problem:

Dynamically sum the cells between size 39 and 50, and put the value in the Pairs (quantity).

Already managed to add the lines, but the result is added to the lines immediately below.

The code that does this operation:

var newTr = $('<tr id="row_' + count + '"></tr>');

newTr.html('<td><input name="product' + count + '" type="hidden" value="' + item_code + '"><input class="span5 tran" name="item' + count + '" type="text" value="' + item_code + '"></td> 
.......
<td><input class="input-block-level text-center" name="sort' + count + '" type="text" value="" id="sort-' + count + '" onClick="this.select();"></td>

<td><input class="input-block-level text-center" name="size39' + count + '" type="text" value="" id="size39-' + count + '" onClick="this.select();"></td>

......

<td><input class="input-block-level text-center" name="size50' + count + '" type="text" value="" id="size50-' + count + '" onClick="this.select();"></td>

<td><input class="input-block-level text-center" name="quantity' + count + '" type="text" value="1" id="quantity-' + count + '" onClick="this.select();"></td>

<td><input class="span2 tran" style="text-align:right;" name="unit_price' + count + '" type="text" id="price-' + count + '" value="' + item_price + '"></td>

<?php echo '<td><input class="span2 tran2" name="cart\'+ count +\'" type="text" value="" required="required" data-error="' . $this->lang->line("cart") . ' ' . $this->lang->line("is_required") . '"></td>';


if (DISCOUNT_OPTION == 2) {

echo '<td><select class="span2 select tran" data-placeholder="Select..." name="discount\' + count + \'" id="discount-\' + count + \'">';

 foreach ($discounts as $discount) {

 echo "<option value=" . $discount->id;

if ($discount->id == DEFAULT_DISCOUNT) {
            echo ' selected="selected"';
        }
        echo ">" . $discount->name . "</option>";
    }
    echo '</select></td>';
}
?>

<td><input class="input-block-level text-center" name="subtotalpares' + count + '" type="text" value="" id="subtotalpares" disabled onClick="this.select();"></td>

<td><i class="icon-trash tip del" id="' + count + '" title="Remove this Item" style="cursor:pointer;" data-placement="right"></i></td>');


newTr.prependTo("#dyTable");
count++;
an++;
total += parseFloat(item_price);

$("input[id^=size]").keyup(function () {
var sum = 0;
$("input[id^=size]").each(function () {
sum += (parseInt(this.value) ? parseInt(this.value) : 1);
});
$("input[id^=quantity]").val(sum);
});

I look forward to some help!
Thank you