Relation in tables

Hello all...
I am starting in Postgresql...
And I have a question:
I am developing a DB system to manage products, but the products may be
separated by departaments (with its respectives coluns)... Like:

CREATE TABLE products(  id   serial  primary key,  desc valchar(100),  ...
);

Okay, but the products is typed by "amount departament" and this departament
should not have access to other coluns like "values, Money, etc...".
The "finances departament" may modify the data into products table, but this
departament should not have access to coluns like "amounts, etc...".

I' ve tried to create the products table with INHERITS but its not right...
look:

CREATE TABLE prod_amounts (  amount_min   numeric,  amount_cur   numeric,  amount_max   numeric,  ...
) INHERITS products;

CREATE TABLE prod_values (  buy_value   money,  sen_value   money,  ...
) INHERITS products;

Okay, but the problem is: I can INSERT a prod_amounts normaly and automaticaly
the products table will be filled, but when i try to modify the data in
prod_amounts (references in products) there is no data....
I think its not right ( I am sure :/ ).
How Can I do it???
How Can I References Between Prod_amounts and Prod_Values automaticaly?
remembering the Amounts departament may not access the Values departament data
and the Values departament may not access the amounts data... And the products
will be registred (typed) in Amount departament....

Thanks for all.