<p><a class="button" href="upgrade.php?action=upgrade"><?php _e( 'Upgrade Network' ); ?></a></p>
<?php
do_action( 'wpmu_upgrade_page' );
<p><a class="button" href="upgrade.php?action=upgrade"><?php _e( 'Upgrade Network' ); ?></a></p>
<?php
do_action( 'wpmu_upgrade_page' );