Search Form HELP + Customised search based on custom_fields and categories

Hello,

I am needing to set up a search form which is based on custom_fields and categories.

So, for example, I have products for sale that need to allow for multiple search options: where a user can select a brand, a size, a price range, location etc. to narrow down the search results.

I have read through the docs for the Search Module, but am not sure how to customise the search form. It seems there are limited tags available ???

Can someone please let me know if it is possible to construct a search form based on various custom_field and category select lists.

Thank you.