Quick question on categories

[Jamesgt]

Just a quick question, hopefully someone can help me. Basically what im trying to do is show all of the listings of the sub category in the main category.
So for example if I had a main Category of Cars and 3 subs as Honda, Nissan, and Toyota.

Cars
--Honda
--Nissan
--Toyota

If the user clicks on Cars I want it to list of all of the listings from the subcats to the main category. I did some searching on the forums and I found this.

open the category.php
Replace

PHP Code:

    $options['section']=$sec; 


with

PHP Code:

    $arr_childs = array((int)$sec);
    $Categories->get_ids($arr_childs);
    $options['arr_childs']=$arr_childs; 


I used it and I thought it worked but it actually shows every listing in all of the main categories. Could someone please help me out with this?

Thanks.