BuddyPress.org

On the top of the activity stream there is a dropdown to show activies that are “Everything”, “Updates”, “Friendships” etc

This is the code in /activity/index.php

<ul>
	<li class="feed"><a href="<?php bp_sitewide_activity_feed_link(); ?>" title="<?php esc_attr_e( 'RSS Feed', 'buddypress' ); ?>"><?php _e( 'RSS', 'buddypress' ); ?></a></li>

	<?php

	/**
	 * Fires before the display of the activity syndication options.
	 *
	 * @since 1.2.0
	 */
	do_action( 'bp_activity_syndication_options' ); ?>

	<li id="activity-filter-select" class="last">
		<label for="activity-filter-by"><?php _e( 'Show:', 'buddypress' ); ?></label>
		<select id="activity-filter-by">
			<option value="-1"><?php _e( '&mdash; Everything &mdash;', 'buddypress' ); ?></option>

			<?php bp_activity_show_filters(); ?>

			<?php

			/**
			 * Fires inside the select input for activity filter by options.
			 *
			 * @since 1.2.0
			 */
			do_action( 'bp_activity_filter_options' ); ?>

		</select>
	</li>
</ul>

Any way to somewhat easily go about adding a button next to it to (also through ajax) update the feed to sort in ASC or DESC order? Really just looking for some key functions or where to start, thanks.