Save Manufacturer as a text in custom field

Configuring a filter scheme I found this bad limitation:

In a text box I can enter text and assign several fields to be matched. This works fine.

But when I write the brand of a product it is not found because the product_manufacturer_id field is storing an id number and not the text name of the brand.

So I should create an extra field where the text of the category gets stored, but how?

I already have the code to show a manufacturer by its name in products listing, is something like this:

	$db = JFactory::getDBO();
	$db->setQuery('SELECT category_name FROM '.hikashop_table('category').' WHERE category_id='.(int)$this->row->product_manufacturer_id);
	$brandName = $db->loadResult();

I don't dare to send you a "Thank you" click until I try this, I never made a plugin but hope is as simple as it looks in the instructions... so we'll stay in contact for this.

thank you for the advice!

Thanks for your support, I will try sometime during this week. knowing your support team is so close it makes me more dareful to try it!