[support] how to associate a node/add form to the node in the URL/loaded?

Hello,

I have a node/add form for a Task node that is loading in a block.

The Task needs to have a node-references automatically made for it (the user shouldn't see it or be able to alter it) that attaches (points) to the node which is being primarily displayed.

So if you are on a Project page, you have the block for add task on the left, and I want this task to point to the Project node. The node is loaded and also in the URL path.

The block that loads the add/Task does:

<?php $form = node_add('project_task'); ?>

Which $form variable do I set in the node/add form to have this default correctly?

I see the variable in the form for the CCK field, just need to know how to associate it... #nid to set? #default_value? I tried #default_value but this doesn't seem to pass forward when rendered.

Thanks for your guidance!

Kindly,

Sebastian.