when a user opens a form to start a process but does not submit - if you want to get a count of this you can do it with a event called task created,check for task status, I think if the task status is 1 then the task is not yet assigned to a user. But if you want to count the number of times a user has opened a form of a submitted task, you can put some code in the render form to capture that action
hope this helps