Post Expirator : show expiration date if set

Hi,
I’m trying to use the “post expirator” plugin.
It works, no problem .

In my template I would like to show the expiration date, but only if it’s set .

If I use the following shortcode, the message apperas even if the post doe not use expiration date.
<span class='dates'> will expire : " <?php echo do_shortcode( '[postexpirator]') ?></span>

Is it possible to display this message only when an expiration date has been set?

Thanks in advance.

http://wordpress.org/plugins/post-expirator/