Hi, 
I'm trying to randomize the order of two blocks. But I also want another block in between those two blocks. 
Here is what I did before (when I didn't need the block in between):

<expt one>
/ preinstructions = (introduction, instructions1)
/ blocks = [1-2 =noreplace(vid_1, vid_1_sl); 3= demographics]
/ postinstructions = (end)
</expt>

Now I tried this, but I could make it work: 

<expt one>
/ preinstructions = (introduction, instructions1)
/ blocks = [1-3 =noreplace(vid_1, vid_1_sl); 2=stroop;  4= demographics]
/ postinstructions = (end)
</expt>

I'm trying to randomize block 1 and 3 without randomizing block 2, as it has to come second. Only the order of 1 and 3 have to be randomized.
Do you have any idea how I have to change it?

Thanks for your help. 

The correct syntax to do this is:

<expt one>
/ preinstructions = (introduction, instructions1)
/ blocks = [1,3 =noreplace(vid_1, vid_1_sl); 2=stroop;  4= demographics]
/ postinstructions = (end)
</expt>