Have you ever thought of using the campaign manager to do this?
Create the item you want to show to a specific user group by using segmentation and using teaser component on the target pages to show/hide the campaign banner if the user falls under a specific group?
Let me give you a brief on how it works:
1. You create a campaign using the '/libs/mcm/content/admin.html' console
2. Create Teasers (this has the actual content you want to show to a specific user group - could be an advertisement banner targeting people below 40)
3. Create Segments and place rules for the segmentation (say like users below age of 40 / even a user group of your choice)
4. Map the campaign created in step 1 to the user group
5. Go to the page where you want to display the campaign banner
6. Drag drop the teaser component onto a parsys where you want the banner to be displayed
7. Configure the teaser component to map the campaign created in step 1.
This way the teaser knows which campaign to display and the campaign knows to which user segment the banner should be dispalyed
Please refer the below link for step by step process of managing campaigns in CQ5;
http://dev.day.com/docs/en/cq/current/wcm/campaigns.html