Drupal 6 hook for field access I want to use my own code to determine if a user has edit access on certain fields.  hook_field_access for Drupal 7 looks right.  Is there a comparable hook for Drupal 6?
A hook with exactly the same name exists for CCK in Drupal 6, it just doesn't seem to be all that well documented.

It's invoked from the content_access() function and has the following signature:

function MYMODULE_field_access($op, $field, $account = NULL, $node = NULL) {

}