Disabling previous steps in GAF roadmap

Hello,

I am using the Guided Activity Floorplan in my application, and I have defined four steps in my roadmap. I noticed that the roadmap displayed on the top part of the window includes links to each of the steps, and it is possible to navigate back and forth between steps using these links. However, in my application, I would like to disable navigation to the previous steps when I am at the very last step. How can I disable the links that show on the roadmap ONLY when I am at the last step?

Thanks,

Kamal