function createbox(){

global $wpdb;
$tablenom = $wpdb->prefix . 'cf7dbplugin_submits';
$requete = "SELECT submit_time, field_value, STR_TO_DATE(field_value, '%d/%m/%Y') AS dtFormat FROM wp_cf7dbplugin_submits WHERE form_name = 'infoCo Configuration' AND field_name = 'date-reunion' ORDER BY dtFormat DESC";
$field = $wpdb->get_results( $requete );
$output99 = '<select name="lstdate" id="fleet" onchange="document.getElementById(\'fleet\').value=this.value;"><option></option>';
foreach ( $field as $ligne ) {

    $output99 .= "<option value=\"$ligne->submit_time\"> $ligne->field_value </option>";

    }
$output99 .= "</select>";
return $output99;
}

$content = do_shortcode( $post->post_content );
$fleet_selector = createbox();
$new_content = str_replace('[autoselectfleet]', $fleet_selector, $content);