Randomizing from multiple groups of answer choices

Hi All --
I am writing a multiple choice question where people will tell me which of three messages they prefer. I have a bank of 30 messages which fall into three themes (10 messages per theme) and what I am really trying to understand is which message theme people prefer.
What I would like to do is to create a series of questions where the set of three messages people are shown generated by selecting one randomly from the ten items in Theme 1, another randomly selected from the ten items in Theme 2, and a third randomly selected from the ten items in Theme 3.
As it stands right now, advanced randomization within a question in qualtrics will let you randomize and pick from a single set of answer choices, but there is no way to say pick 3, one from each of these sets.
Is there any chance that custom code could help me do what I want? Just writing lots of different questions and randomizing at that level doesn't work, since it would mean creating 10 x 10 x 10 permutations.