I maybe unclear of what you require? Apologies if this is the case.
Assume you have Q1 and Q2 and you would like to randomly select one of these questions.
Assume you have Q3 and Q4 and you would like to randomly select one of these questions.
So you would like to ask two question (one from each question set) with the possible options available ...
Q1 and Q3
Q1 and Q4
Q2 and Q3
Q2 and Q4
Q3 and Q1
Q4 and Q1
Q3 and Q2
Q4 and Q2
Try this technique ...
Go to Randomize / Blocks and define Set 1 which contains 4 blocks with anchors set as follows ...
Select the "Use Constructed List" option at the bottom and select "Set1ConList" which I have listed below.
Setup a parent list called "BlockList" ...
Setup a constructed list called "SetAConList" (uses the parent list "BlockList") ...
Setup a constructed list called "SetBConList" (uses the parent list "BlockList") ...
Setup a constructed list called "Set1ConList" (uses the parent list "BlockList") ...
SetAConList randomly selects 1 or 2. SetBConList randomly selects 3 or 4. Set1ConList collates SetAConList and SetBConList and randomises.
So we now have randomising WITHIN sets and randomising OF sets.
I have just tested this out and works fine. Hope it's what you are after Hanley.
Note - this would work fine with single questions (as this example displays) and also subsets of questions. The anchors in Set 1 would change as would SetAConList and SetBConList.