Hi,
Modifying files directly are not recommended, you wouldn't be able to update HikaShop without loosing your modification after that.
Modifying the helper file is highly not recommended, for same reasons.
We have a very good plugin system and you can add new blocks in the backend order form using the trigger
onAfterOrderProductsListingDisplay(&$order, $type);
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.