UPS Total Weight packege

-- HikaShop version -- : 3.4.0
-- Joomla version -- : 3.8.6.
-- PHP version -- : 7

Hi Hikashop team,

I'm busy creating a CSV export for UPS Worldship software.
UPS need the weight of the total package in kg.
(In our case it's always the total weight of the order.)

But I can't find a field in the Mass Action to export the total weight.
Can you please give me a hint how to get this value.
I can create a custom field order_total_weight I don't know how to update the value in this field.

Hope you can help me.

Kind regards,
Lumiga

Oké thanks!