Sub-totals for Survey Questionnaire

What is the best way to display a sub-total for specific statements on a survey questionnaire?  For instance, I have survey with 15 statements (labeled a thru o).  Each statement can have a response of 1 - 5 (1=Always, 5=Never, etc.).  I need to get sub-totals for specific statements on the list.  For instance, what is the score for statements a, e and n?  Or for c, g, and m?  Sorry if this sounds complicated, but it's a pretty standard survey questionnaire format/result exercise.  I'm sure someone out there has already done this in Storyline!  Thanks ...