zencart 1.39f with COWOA

I am trying to install, but during merging I come up with the following.

in the file includes/classes/order.php there is this line

Code:
if ($_SESSION['COWOA']) $sql_data_array[COWOA_order] = 1;
which should be replaced by

Code:
//Multisite Module - Add the order_site in the order table
$sql_data_array['order_site']=ORDER_SITE;
//eof Multisite Module
But if I do that i am afraid it will ruin COWOA.

Please advise on how to proceed