Exclude a vendor from the Advanced Search function?


I am trying to work out how to exclude a vendor from appearing from the list of sellers in the Advanced Search - does anyone know if this is possible?

I think the relevant code is found in view/products/components/product_search_form.tpl and is:

<div class="form-field"><br />
		<input type="hidden" name="company_id" id="company_id" value="{$search.company_id|default:''}" /><br />
		{include file="common_templates/ajax_select_object.tpl" label=$lang.search_by_vendor data_url="companies.get_companies_list?show_all=Y&search=Y" text=$search.company_id|fn_get_company_name result_elm="company_id" id="company_id_selector"}<br />
```<br />
<br />
In particular, the "show_all=Y" but am stuck as to where to go from there - any pointers anyone has would be much appreciated!<br />
<br />
Thank you<br />
<br />