Help needed enforcing constraints..

Hi Netters

.. I am trying to enforce a constraint on making sure that an order number is entered in correctly.. IE.. It must have format values [A-Z][A-Z][A-Z][0-9][0-9] in order to be a valid number. so if someone were to enter in an order number as lets say bmss3  or b3m91 they would get an error msg..becuase the correct format would have to be bms99 in this case. Now I have figured out how to do this in a model example below..but it is very poor since I had to make each character a different attribute and enforce the constraints one at a time..and in the long run I would end up with a huge concatenated primary key...
  Is there a way to enforce a constraint such as the value entered must have the format of [a-z][a-z][a-z][0-9][0-9] when it is entered in by the user? Can I do this at the create table level command?? thanks for the help!!..Dan

create table customer2
(first_pos char(1) not null constraint first_pos check
(first_pos between ('A') and ('Z')),

  second_pos char(1) not null constraint second_pos check
(second_pos between ('A') and ('Z')),
  first_num number(1) not null constraint first_num check
(first_num between (0) and (9)))

-- 
Dan Roberts
BRISTOL-MYERS SQUIBB PHARM. RES. CENTER      "Nature is last at Bats"
PRINCETON, NEW JERSEY U.S.A. PLANET EARTH, MILKY-WAY GALAXY
<<<<INTERNET ADDRESS>>>>Roberts_Daniel_G.PriLVMS3_at_MSMAIL.BMS.COM