I am going to propose an alternative approach to achieve your goal, which if I understand correctly is sending out an email to a site visitor who doesn't reach a desired state.
1 - Set up Marketo's Munchkin tracking code on your website. It works similary to Google Analytics by tracking page visits on your website, but it also provides additional functionality because you are tracking activity on an individual user.
2- Set up a smart campaign in Marketo to run on one person at a time based on live events by adding Triggers. For example, people who visited certain pages (ex: shopping cart) but did not visit other pages (ex: checkout page)
Please let me know if this approach makes sense?