Is it possible to do semi-randomization for 6 blocks?

Hello!
I am currently designing a survey in which participants will view 3 sets of paired blocks (total of 6 blocks). I want to randomize the order of the blocks that they see, but ensure that paired blocks are never viewed directly before or after the other pair.
For example:
If we have blocks A1, A2, B1, B2, C1, C2
An example of an appropriate order would be: A1, B1, C2, A2, B2, C1 or A2, C1, B2, A1, C2, B1
However, we want to avoid the following: A1, A2, B1, C1, B2, C2, B1 (because A's are viewed consecutively) or A1, B2, B1, C1, A2, C2 (because B's are viewed consecutively).
Would this require custom code? If so, any assistance/direction would be greatly appreciated!
Thank you in advance for any help!!