I created a form and what I wanted was a "Sum" at the bottom based on choices made above. So for instance if they approve the formatting then the score goes up by 25... if they like content then the score goes up by 25... (100 possible). I used Yes/No for two choices and the other choice is 1 of 5 check boxes (Excellent, good, etc.). However, if they first pick yes (say for formatting) and then change their mind and choose no it has already added the 25 to the score at the bottom. Also, if they go back and choose yes a second time then it adds the 25 a second time.
What is the best way to avoid this type of error?