Drupal 6 CCK fields export/import in between environments
Take a look at the Features module. Exporting your CCK fields as a feature set creates a new module in which the fields are defined in code. You can then deploy the code to another server and enable the feature there. Every time you make a change you export the feature again to update its code, deploy it, then revert it on the other server.

Features is very useful, but takes some practice to get used to its limitations and quirks. Once you get past that point it'll save you a lot of time.