[development] Making custom fields available to CCK administration menus

Hi, this is Karl Giesing, aka Karlheinz. I'm the developer of the Discogs module: http://drupal.org/project/discogs I have a user who uses CCK, and would like to administer the fields I created, using CCK's "Manage Fields" and "Display Fields" menus. I did NOT create the fields using CCK, and was wondering if this is possible. Any ideas? I haven't found any documentation on how to do this. -Karl.