Get products in an order

Hi,
I've implemented the post-processing hook as per this blog post (http://www.sitefinity.com/blogs/teresamiller/posts/11-10-04/the_power_of_post-purchase_processing_hooks_in_ecommerce.aspx). It's all working well so I can get the data from Sitefinity into our 3rd party software.
However, I want to be able to send out a specialized email whenever a product thats in the Events department (which we created) is purchased. I have the email working fine. I just need to know how to look through the order and determine if a product in a specific department was purchased in that order. If so, send the email.
Suggestions?