Newsletter addition

(I accidentally posted this in Addons at first, i thougt the newsletter system was an addon but i found out its not.
So i post this here as well. My apologies for that.)

I would like to add a selection in the audiences_list via the query_builder table.

The addition is that i want to select newsletter subscribers who live in a certain country. For each country i choose i want to add a row in the query_builder table. The country is determined in the address_book table by a certain id.

For example, the query should give me all newsletter subscribers that live in the country with the id 150 (Netherlands).

Th standard query in the query_builder table for newsletter subscribers is:
select c.customers_firstname, c.customers_lastname, s.email_address as customers_email_address from TABLE_SUBSCRIBERS as s left join TABLE_CUSTOMERS as c on c.customers_id = s.customers_id

I'm not that familiar with sql queries to expand it myself.
Could anyone help me out here please?

Thanks in advance and best regards,
Marcel van Vugt.