URL search strings

We'll be using alot of custom html on our site. We often include URLs which submit searches. I know I can submit a search in a URL like this:

<a href="http://watchprince.explorewebdev.com/s.nl/sc.2/.f?search=black">black</a>
(finds all black items on our website)

I want, however, to narrow that search. For instance, if I want to find only black leather items, I can add +leather, like this

<a href="http://watchprince.explorewebdev.com/s.nl/sc.2/.f?search=black+leather">black leather</a>

Problem is, this searches the entire website and I end up with black leather watch boxes, watch winders, watch bands, etc. Let's say I only want Watch Bands. If I add +watch+bands to my search string, I still get boxes and actually lose some watch bands.