Password Protecting a Category URL?

I don't know if this is really doable with ZC but here's my dilemma. I have a series of categories to my store and two of them need to be password protected so not everyone can shop in this section of the store. For example:

http://www.jamwestfoods.com/store/index.php?main_page=index&cPath=5

Is open to everyone.

http://www.jamwestfoods.com/store/index.php?main_page=index&cPath=6

Is supposed to be password-protected before you can see the content in this area since it's for wholesalers only and the items are different to boot.

So is it possible to assign a password prompt to appear when someone tries to attain this URL?

This would take some customization to control all of the products being displayed everywhere so that unless logged in and marked as a wholesaler no one can see the products in any section for New, Sales, Specials, Featured, Upcoming, Also Purchased etc. etc.

This would take a bit of thought, but it can be done ...

What version of Zen Cart are you running?

I'm using 1.3.8. So it's the latest as of 9/21/08.

I did check out some similar threads and found this one:
http://www.zen-cart.com/forum/showthread.php?t=88819&highlight=password+protect

and followed the code where I inserted:

if (!$_SESSION['customer_id'] && ($cPath_new = '6')) {
$_SESSION['navigation']->set_snapshot();
zen_redirect(zen_href_link(FILENAME_LOGIN, '', 'SSL'));
}

prior to:

return 'cPath=' . $cPath_new;

on the file: /includes/functions/functions_categories.php

But it didn't change anything. I uploaded the new file and clicked on Wholesale-->Retail which takes you to http://www.jamwestfoods.com/store/index.php?main_page=index&cPath=6

and nothing changed. Took me right to the page. Which isn't what I want at all.