Millisecond Forums

Dear all, 
I have been working on an Inquisit script (please find it attached) and I am struggling with the stimuli selection.
I have a block with four different types of trials: approaching stim_1 in the upper part of the screen with distractor_1; approaching stim_1 in the lower part of the screen with distractor_1; approaching stim_1 in the upper part of the screen with distractor_2; approaching stim_1 in the lower part of the screen with distractor_2. 

There are eight stimuli by category (ie eight stimuli for stim_1 ; eight stimuli for distractor_1 ; eight stimuli for distractor_2) and overall, I would like to display 128 trials (32 per type of trials). I also would like that, at the block level, each possible pair of stimuli (64 pairs = stim_1 with distractor_1 and 64 pairs = stim_1 with distractor_2) would be displayed only once, with stim_1 being randomly displayed either in the upper part of the screen or either in the lower part of the screen.

I have mainly used this post to compute the actual code : https://www.millisecond.com/forums/Topic2273.aspx

Any help would be greatly appreciated! Thank you very much,
warm regards,
S.M