Decreasing point value based on elapsed time

Hi,

I'm building a Jeopardy!-like game/quiz in Storyline 3 and would like to set it up so the quicker a user answers the question correctly, the more points they earn (or more accurately, the more time it takes, the less points they earn). There are 6 clue categories and 5 clues each (worth 100 through 500 points) so I've set up 30 question draws and results slides and will display cumulative results at the end and send the cumulative results to LMS.

I've figured out how to use the question timeline to set a number variable to use as a multiplier - default value is 1, at 1 sec it is changed to .84, at 2 sec it is changed to .68, at 3 sec changed to .52 and so on. I'd like to multiply the question correct point value by this variable to define the final score for each question bank. I understand the Results.ScorePoints variable is read-only; any thoughts on how I might accomplish this? I've attached my .story file. Thanks

Matt