It depends on which country issued the JAA licence to which wish to transfer the rating. Assuming that your JAA licence was issued by Norway, you will have to find out what the Norwegian CAA's requirements are.
In the UK, to transfer a 737 type rating to a JAA licence without further training, you must have at least 500 hours on type, operational experience within the preceding 5 years and pass a Proficiency Check with a JAA authorised examiner. The requirements in other JAA member states may be different.