Update Permalink when Custom Taxonomy is Selected

Hi,
I’ll try to illustrate the situation the best I can.

Let’s assume that we have the following permalink structure for a “regular” post:

/%category%/%year%/%monthnum%/%day%/%postname%/

Now 2 things can happen with this scenario:

1) you introduce the title of the post and no category is selected, your temporary URL would be:
/uncategorized/2012/01/01/post-name/

2) you select a category and then you introduce your title, the result would be:
/selected-category/2012/01/01/post-name/

I realize that this is done via AJAX, but how? is it a filter?

I have a Custom Post Type and Custom Taxonomy permalink structure like this:
/custom-post-type/custom-taxonomy/post-name

And I would like to achieve Option 2, but for my permalink structure I’ve been only able to do it when the post_status changes to “publish” or “draft” using the following function:

http://pastebin.com/FCeMjjdg

Any pointers on how to achieve option 2 for my Custom Post Type permalink structure via AJAX would be greatly appreciated.

Thanks.