[Plugin: NextGEN Gallery] button for next and previous slideshow images (no Flash)

I’d like to add an HTML next and previous button to my PHP template that will move to the next (or previous) image in the slideshow.

My existing slideshow code is:

<?php echo do_shortcode('[slideshow id=1 w=558 h=294]'); ?>

What can I add to these tags to trigger the slideshow movement I want?

<a href="#">Previous</a>
<a href="#">Next</a>