Shipping restriction using Warehouse

-- HikaShop version -- : 2.3.2
-- Joomla version -- : 3.3.3
-- PHP version -- : 5.4

I managed to use a warehouse A to restrict a particular shipping method A to the product associated to that warehouse A.
Now I would need to restrict another shipping method B to any warehouse (or no warehouse) except warehouse A.
Basically to have an excluding function in the restriction rather than an including function.

How could I reach such functionality?
Thanks.

Max

Hello Max,
You'll be able to do that by developing it which will require some development skills, or by including a different warehouse.

I cannot include a different warehouse as I need a rule to exclude 1 specific warehouse and allow all the others or no warehouse at all.

So I guess, I can try to develop my first plugin based on Hikaship Manual Shipping plugin.
But when I look in the folder /plugins/hikashopshipping/manual the file manual.php just mentions
class plgHikaShopshippingManual extends hikashopShippingPlugin {
var $multiple = true;
var $name = 'manual';
}

Do you know where I can find the code of manual shipping plugin?