Change state of a button to normal after layers have been viewed

Hey everyone.  I've seen this topic discussed numerous times in various threads; however, none of the approaches resolve the issue I'm having.  Have I just been looking at this project for too long, or am I just really that daft?  Please help!

Here's the gist of how this slide should flow:

1. When the user gets to this slide, they have 3 buttons on the bottom that say, "Avoid"
2. When the user clicks the button, it stretches out to expose the topic and they are taken to that layer to learn more about the topic
3. After the user has viewed all 3 layers, a "Back to Scenario Button" should pop up which takes the end user back to the scenario tree from whence they came.  This is where I'm getting stuck.

Here are the parameters from the client:

• The end user must view all layers in order to return to the scenario tree.
• It must be layers, not additional slides or lightboxes.
• The client wants the end user to have the freedom to choose the layers in any order they want, but must return to the base layer automatically after viewing each layer.
• The client has requested that the scenario tree button be hidden (as opposed to 99% transparency) until all conditions are met because "the end user might accidentally hover the mouse over the button, therefore changing the mouse icon," or "the end user might have eagle vision." :)
• The base layer must be covered by the background images of the new layer.
• The client wants the end user to have the option to review the layers again, either before leaving the base slide or after returning from future slides.

DEVELOPER'S NOTE:  You'll notice in the Trigger Menu a Passive Behavior Button but no Passive Button content in the slide.  This is because "Passive Behavior" was later renamed "Dead End Phrases" by the client.

Thanks in advance for your help!