[development] Custom form to create multiple related CCK nodes

I need a form which will allow users to create several related CCK nodes at the same time. Node (a) will include a filefield. Node (b) will need to refer to node (a) using a nodereference field. I would like to use as much of CCK's built-in validation, submission, input widget, and security functionality as possible/practical. It seems that I should either create a custom form from scratch, or concatenate and manipulate the 'normal' node creation forms for the relevant content types. What is the best way to accomplish this in Drupal 6? Several CCK gurus have warned against using drupal_execute for this purpose, so I'd like to stay away from that. Thank you very much for your help!