How can i build a search with checkbox

Hy guys,

how can i build a search with checkbox.

Post type: locatii.

<form method="get" name="searchform" action="<?php bloginfo('url'); ?>/">
<input type="text" value="<?php the_search_query(); ?>" name="s"/><br>
<input type="checkbox" name="tip" value="locatii">Tip 1<br>
<input type="checkbox" name="tip" value="locatii">Tip 2<br>
<input type="checkbox" name="tip" value="locatii">Tip 3<br>
<input type="checkbox" name="tip" value="locatii">Tip 4<br>
<input type="checkbox" name="tip" value="locatii">Tip 5<br>
<input type="checkbox" name="tip" value="locatii">Tip 6<br>
<input type="checkbox" name="tip" value="locatii">Tip 7<br>
<input type="submit" name="search" value="<?php _e('Search'); ?>" />
</form>

In the post type i have categories, Tip1, Tip2, Tip3…

So wath i want to get the result base on selection.

Example: i select tip 2, tip 5 – i get all the results that are in that categories.( tip2,tip5)

Thanks.