Just a quick one, why don't you use OOB appointments to capture visits made by them. Create a new field like a two option set to identify if that appointment lead to creation of an appointment.
You can always create a custom activity to map this. However its always advisable to use OOB functionalities.
Hope it helps!
Regards, Abhishek Bakshi If you find this post helpful then please Vote as Helpful and Mark As Answer. Check my blog on https://mydynamicscrmblog.wordpress.com/