Inserting data from one database to another using stored functions

Hi pgSQL peeps!

I'm stumped on this question for over 3 days now.

I need to run a stored function in Database A ("sf DBa") which calls a
stored function in Database B ("sf DBb").

Here's "sf DBa":

CREATE OR REPLACE FUNCTION sp_update_serialnumber(pserialnumber character
varying, pActivityId integer)

RETURNS void AS

$BODY$

BEGIN

UPDATE TABLESSERIALNUM SET SerialNumber = pSerialNumber
WHERE ActivityID = pActivityId ;

BEGIN

PERFORM dblink_connect('dbname=testdb
port=5432 user=postgres password=123456');

PERFORM dblink_exec('SELECT
sp_insert_detailtable('|| pActivityId ||', '|| pserialnumber ||')');

PERFORM dblink_disconnect();

END;

END;

$BODY$

LANGUAGE plpgsql VOLATILE

COST 100;

Here's "sf DBb":

CREATE OR REPLACE FUNCTION sp_insert_detailtable(pactivityid integer,
pserialnumber character varying)

RETURNS void AS

$BODY$

BEGIN

INSERT INTO DETAILTABLE(LogID, LogDetailSeq)

VALUES(pactivityid, pserialnumber);

END;

$BODY$

LANGUAGE plpgsql VOLATILE

COST 100;

I'm using the DEBUG function in pgAdmin, and I keep getting the "statement
returning results not allowed" error in PERFORM dblink_exec('SELECT
sp_insert_detailtable('|| pActivityId ||', '|| pserialnumber ||')'); in this
line.

Your help is highly appreciated!

Thanks and Best Regards,

Benjie