X-Cart forums - Subcategories Listing help!

Im currently trying to implement a shop by brand section in a drop down menu.

Code:

<FORM action="home.php" method=GET name=cat_form>

<SELECT name=cat onChange="javascript: document.cat_form.submit()">

{section name=cat_num loop=$subcategories}

<OPTION value="{$subcategories[cat_num].categoryid}"{if $subcategories eq $subcategories[cat_num].categoryid} selected{/if}>{$subcategories[cat_num].category}</OPTION>

{/section}

</SELECT>

</FORM>

but the above once into a category it will then list the subcategories, but i just want the subcategories to be displayed under the specific cat.
what I require is for the main cat i created (ie. shop by brand) just to display the its subcategories subcategories

I have tried to include a if statement

Quote:

{if $config.general.root_categories eq "351" loop=$subcategories}

in the form
but that just gives me a smarty php error of an unexpected $

any help would be grateful.

many thaks
Anton
http://www.savatrader.com/xcart/customer/home.php