X-Cart forums - Sub-Categories in Advanced Search Dropdown???

Okay, where do I channge the bolded loop to list subcategories in the dropdown as well?

Code:

<select name="in_category">

<option value="">All</option>



{section name=cat_num loop=$categories}<-------------- Need to edit the SQL Select for this loop



<option value="{ $categories[cat_num].categoryid}" {if $smarty.get.in_category eq $categories[cat_num].categoryid or $cat eq $categories[cat_num].categoryid}selected{/if}>{$categories[cat_num].category|escape}</option>

{/section}

</select>

Any help is appreciated, because as it stands now the drop-down is only displaying the top-level categories.