Block randomization question

I'm having trouble getting my questionnaire file set up to do the block randomization I'm looking for. I have 20 sets of questions, each with 6 items presented in groups of 3: (a, b, c) or (d, e, f). I want to present participants with one of the (randomly chosen) groups of 3 for [I]each[/I] of the 20 sets.

So each participant should get either (1a, 1b, 1c) OR (1d, 1e, 1f), either (2a, 2b, 2c) OR (2d, 2e, 2f), etc., all the way down to either (20a, 20b, 20c) OR (20d, 20e, 20f).



I also would like to randomize the order in which they see the 20 items, so participant 1 might get:
(14a, 14b, 14c); (3d, 3e, 3f); (8d, 8e, 8f); etc.

...and participant 2 might get:
(2d, 2e, 2f); (19d, 19e, 19f); (10a, 10b, 10c); etc.

Does that make sense? I'd rather not have to make each set of 3 questions (e.g., 1a, 1b, 1c) into a separate questionnaire, because then I would need 40 questionnaires just for this randomization!

Any suggestions on how to do this?

I don't see a way around using multiple que files here because you can't use multiple levels of BGR within a single questionnaire file. But on the plus side, it ought to only be 20 not 40.

You could place all six items for a group within a single que file. You assign the abc items a BGR value of 1 and the def items a BGR value of 2. On the c and f items, you use a [I]skipto[/I] value jumping them to an end item in that questionnaire (e.g., a simple blank instruction item with a (d1) parameter). That takes care of which three they see from the six. Then you just randomize the order of those 20 [I].que[/I] files in the experiment ([I].exp[/I]) file.