Problem adding columns

I have two tables, from one of which I wish to obtain the sum of several
columns (return1,....return7) and insert the result into the other.

Here are the tables layout:

CREATE TABLE investments
(
investment_id serial NOT NULL,
client_id integer,
client_number integer,
investment_date date,
investment_amount integer,
return1 integer,
return2 integer,
return3 integer,
return4 integer,
return5 integer,
return6 integer,
return7 integer
)

CREATE TABLE totalreturns
(
client_name character varying(128),
initial_invest numeric(8),
total_reimburse numeric(8),
difference numeric(7)
)

And the function to perform the aforementioned calculation:

CREATE FUNCTION
add_reimburse(integer,integer,integer,integer,integer,integer,integer)
RETURNS integer AS $$
DECLARE
sumyields investments%rowtype;
yields integer;
client_count integer;
counter integer;
BEGIN
SELECT count(*) INTO client_count FROM investments;
FOR counter IN 1 TO client_count
LOOP
yields:=
sumyields.return1+sumyields.return2+sumyields.return3+sumyields.return4+sumyields.return5+sumyields.return6+sumyields.return7
;
INSERT INTO totalreturns(total_reimburse) VALUES(yields);
yields:=0;
END LOOP;
return counter;
END;
$$ language plpgsql;

The code is not resulting in any calculations inserted on the "recipient"
table totalreturns.

Thank you in advance for any suggestions.

--
Regards

Oscar Alberto Chavarria
Mobile: +506 814-0247