How do I add subtitles to a Constant Sum question

I have a constant sum question and I need the total across all answers to be 100.

I have sub categories within the question that I would like to label with a title - how do I add a title so that the question looks as follows?

Overall Question
_Sub-Category Title_
Answer 0
Answer 0
Answer 0
_Sub- Category Title_
Answer 0
Answer 0
Answer 0

Any help would be greatly appreciated!

Thanks,

Calum