Drupal 6: cck form that fetches from webservice dynamically

Answer 1

Drupal Pro Development has an excellent chapter on AHAH. A free resource is DrupalSN.

However, trough CCK things will become a little more complex.

ClientJs -> Drupal-GET -> remoteserver XML/Json/? -> Drupal -> FAPI -> Json/HTML -> Client

is the usual call stack for AHAH. AHAH is actually misnamed in Drupal, since it only works trough the FAPI.

You would be looking at something like:

CCK -> FAPI -renders-> ClientJS -> Drupal-GET -> remoteserver XML/Json/? -> Drupal -> CCK-hooks(s) -> FAPI -> Client.

The hard part is to use the CCK-api to add JS aha calls to items and on the other side, to make Drupal fetch the AHAH and run it trough the CCK-API in order to change the FORM, rather then have Drupal render the form with FAPI outside of CCK (FAPI, is Form API).