Qualifying for the audience and test when an element on the homepage is clicked on

I want to create an A/B test for visitors who click on a specific link that will redirect them to the activity url.

Let's assume that visitors who click on a button that reads 'Shop Cars' on the homepage will redirect to a page that displays a  listing of cars. I want to create a test where half of the visitors who clicked on my button will instead redirect to a page that contains curated assortment of cars from a specific brand.

The issue that currently exists is that visitors have more than one way to qualify for my activity. They are currently able to redirect to the activity URL by clicking on the 'Shop Cars' link on the navigation menu, but I specifically would only want to track the visitors who clicked on the button located within the homepage. 

In regards to metrics, I would want to measure the number of car listings viewed for visitors who only clicked on my button on the homepage.

Is there anyway for me to pass a parameter or an indicator inside the Audience Rules of my test to check whether or not the visitor has only clicked the homepage button instead of the link on my navigation menu?