activate carrier just for selected products

[TomRo]

I automatically import all items from my supplier (each 5 seconds)
I have my own warehouse

I want to send the products from my warehouse with X carriers, which cannot be sent with the carriers that my supplier synchronizes

Various problems:

1. If I create the carrier and assign it to Europe, I have the same shipping price for Spain as for Germany since I would could not filter it -> you will say,  move the countries to a new area and so you can distinguish them ... ERROR then the carriers of my provider would not work in the countries that were moved (I do not know if that country could be copied to a new area ??)

2. If I create the carrier and can arrange to distinguish the price of the different countries, the products that you select from my supplier, it will come out that you can buy them with my carrier too ... -> solution, deactivate my carrier for all products, select manually (in the Transport section within the product) my carrier in whose products that i want

I can think of infinite problems, but I can't think of solutions ... please, any help?