Javascript to update quiz score

Here's what I'm trying to do:

Using regular slides, I've built a pre-test for my course that allows the learner to demonstrate proficiency in the courses objectives and skip over those portions that they already know.  I'm accomplishing this by having the button for the correct answer update a variable for the associated objective.  I've also set this up for the test, which I used quiz slides for, so that the learner would skip over questions they've already demonstrated proficiency in.  To get a final test score, the correct pre-test questions also update the quiz score.  The problem is, that this means I could end up with scores over 100.

Here's what I'd like to know.  I want to use the variable to make a decision about whether or not to give quiz credit based on whether or not they demonstrate proficiency.  Example, if they learner has to get 6 or 8 questions corrected, I'd like to build an advanced action that says    If <variable> is equal to or great than 6, the multiply <variable> by 5 and add to quiz score.  This way, if the learner doesn't demo proficiency in an objective, they don't get any credit for the pre-test answer for that objective.

I'm thinking that I need to use JavaScript to make this happen, but any suggestions would be greatly appreciated.

v/r

Jay