Complicated Block Randomization Issues

I have an IAT set up with 4 blocks. I am trying to randomize the blocks in a specific way, but I'm not sure if this is possible in Direct RT. First, I would like for blocks 1 and 2 to be presented before 3 and 4, but I want to randomly select whether 1 or 2 is presented first. In other words, it would present either 1 or 2, then whichever of those was not presented, then either 3 or 4, then whichever of those is not presented.

Additionally, I would like to randomize block order by subject. For odd-numbered subjects, I would like blocks 1-2 presented before blocks 3-4 and for even-numbered subjects, I want 3-4 presented before 1-2. I'm not sure if this is possible. One solution I've come up with if it's not possible is to just use different input files for even- and odd- numbered subjects.

However, I still have not come up with a way to acheive the first randomization (randomizing the 4 blocks, but first 1-2 and then 3-4). Thanks for you help!

The by-subject assignment would have to be done with seperate input files. I think the block assignment also would have to be done as a betweeb subjects factor--i.e., by assignment of different input files. Off hand I don't know of an easier way to handle that particular constraint.