How can I combine this php statement to get the results of multiple variable inputs?

If you are using WP 3.1, I would recommend using the meta_query parameter with the WP_Query class.

$args = array(
    "meta_query' => array(
        array(
            'key' => $customkey1,
            'value' => $customvalue1,
            'compare' => '='
        ),
        array(
            'key' => $customkey2,
            'value' => $customvalue2,
            'compare' => '='
        )
    )
 );
$query = new WP_Query( $args );

if ( $query->have_posts() ) : 
    while ( $query->have_posts() ) : $query->the_post();
        the_title();
    endwhile;
endif;

The meta_query parameter allows for very powerful queries with metadata.

Sources:

http://codex.wordpress.org/Function_Reference/WP_Query#Custom_Field_Parameters