How to add a custom widget to a node creation form Drupal 6 This may be a dumb question, but nothing I could find really told me what I was looking for. Without furthur ado:
I need to add a custom widget that will edit node reference fields on CCK content types. This widget needs to show up in the node creation form, and should consist of a textbox and a button. When the button is clicked, the widget should take the contents of the textbox and use it to create a new node of a different content type and then store a reference in the field it edits. 
I need the D6 hooks which I need to implement this. Links to their documentation would be helpful.
I'd take a look at two modules, the base level Hierarchical Select module and its Hierarchical Select Node Reference submodule.  The second module allows you to create "on the fly" a node referenced by the parent node being created and may do what you need without custom coding on your part.