Recording first selection in a freeform slide

I have a course with multiple freeform quiz slides. The way the course is designed the learner can return to previously viewed slides. How can I set the course to record and assign point values to the FIRST selection made on a freeform slide. For example, the learner selects the wrong answer, moves forward through a few more slides, then goes back and selects the correct answer. How can I prevent the course from overriding the learners first selection?