Searchform changes don’t work

I’m trying to show the items in the search area as a checkbox instead of a pulldownlist. The categories are now alltogether in one list, but I want visitor to have the option to select more options.

First of all I tried to add the sample code to the functions.php in the template folder. Unfortunately I don’t see any changes to the search area. Can somebody help me with that first step?

Added this to functions.php

add_action('em_template_events_search_form_ddm', 'my_em_styles_search_form');
function my_em_styles_search_form(){
    $my_em_styles = (is_array(get_option('my_em_styles'))) ? get_option('my_em_styles'):array();
    ?>
    <!-- START Styles Search -->
    <select name="style">
        <option value=''>All Styles</option>
        <?php foreach($my_em_styles as $style_id=>$style_name): ?>
            <option value="<?php echo $style_id; ?>" <?php echo ($_POST['style'] == $style_id) ? 'selected="selected"':''; ?>><?php echo $style_name; ?></option>
        <?php endforeach; ?>
    </select>
    <!-- END Styles Search -->
    <?php
}

function my_em_styles_accepted_searches($searches){
    $searches[] = 'style';
    return $searches;
}
add_filter('em_accepted_searches','my_em_styles_accepted_searches',1,1);