[Plugin: Google Maps v3 Shortcode] php strings in shortcode?

I installed this plugin for my business directory. Currently each local business has their own page, and I wanted to add the map to it.

The pages are outside of the loop so I have had to use this instead of the shortcode:

<?php echo do_shortcode('[map marker="yes" infowindow="<strong>Title</strong>"]'); ?>

What I want though is to be able to add strings into this shortcode, for example I have the title in a string called $wpdir_title which I would want to go in the infowindow.

How would I go about doing this?

http://ww.wp.xz.cn/extend/plugins/google-maps-v3-shortcode/