primary key

hello,

i have a question about the PRIMARY KEY,
how can we let it start from for example 1000 instead of 1?

This is our program:
CREATE TABLE hy3_pack
(
hy3_id serial NOT NULL,
hy3_serie_nummer text NOT NULL,
hy3_barcode text NOT NULL,
hy3_type_vulling text NOT NULL,
hy3_tarra_gewicht text,
hy3_artikel_id numeric NOT NULL,
hy3_refill boolean,
vernietigd boolean,
opmerking text,
CONSTRAINT hy3_pack_pkey PRIMARY KEY (hy3_id)
)
WITH (
OIDS=FALSE
);
ALTER TABLE hy3_pack OWNER TO postgres;

what must i change in my program?

Met vriendelijke groeten,
Peter Evens
BANDIT nv/sa
Nijverheidslaan 1547
B-3660 Opglabbeek
België
Tel. 0032/89/85.85.65
Fax 0032/89/51.85.47
peter(at)bandit(dot)be