How to pass a node reference from one node to another using CCK Node reference Autocomplete default value

From the node you would like referenced, or from a block that displays on that node do something like this:

<p><a href="/node/add/node-type-to-be-created/<?php $id = arg(1); print $id;?>">Click here to create a new node that will have an autocomplete that will reference this node</a></p>

This will add the node id to the url so it can be captured by the new node.

Then using cck node reference field of autocomplete type, place the following in the "default value" section to provide the default value, which will be the node that referenced the creation of this node

$id2 = arg(3);
$mynode=node_load($id2);
return array(
0 => array('nid' => $mynode->nid)
);

This will capture the node id from the url and feed it into the autocomplete field.

If you don't want the autocomplete field to display, you can easily hide it using css.