SelectCreditItems.php Posting Cost

[daveparrish]

I am trying to post the cost of an item when posting a credit I know this is odd but we have some free items that we give a credit for and do no know the cost until we post the credit.
Here is what I have so far
Around line 586 I have added this line
$StandardCost = filter_number_format($_POST['StandardCost_' . $LineItem->LineNumber]);
And around line 700 I have added
<th>' . _('Cost') . '</th>

And around line 742
<td><input type="text" class="number" name="StandardCost_' . $LineItem->LineNumber . '" size="8" maxlength="10" value="' . locale_number_format($LineItem->StandardCost,$_SESSION['CreditItems'.$identifier]->CurrDecimalPlaces) . '" /></td>

It post the standardcost in the line if the item has a standardcost but I will not updated the standardcost.
Any help would be greatly appreciated.