Hello, 
I am doing an evaluative conditioning script in which I would like 12 faces (CSimages) to be randomly matched: 4 with neutral images (setup_neutral) and 8 with positive images (setup_positive). Before the pairs are presented on the screen 8 times each. I really can't do it. Could you help me, please?

ps : the link will give you access to all the images used in this code

Here is my code:

<picture CSevaluation>
/position = (50%,20%)
/size = (30%,30%)
/items = CSimages
</picture>

<item CSimages>
/1= "Face1.jpg"
/2= "Face2.jpg"
/3= "Face7.jpg"
/4= "Face12.jpg"
/5= "Face22.jpg"
/6= "Face58.jpg"
/7= "Face60.jpg"
/8= "Face64.jpg"
/9= "Face67.jpg"
/10= "Face75.jpg"
/11="Face77.jpg"
/12= "Face89.jpg"
/13= "Face93.jpg"
/14= "Face99.jpg"
/15="Face107.jpg"
/16= "Face130.jpg"
/17= "Face138.jpg"
/18= "Face139.jpg"
/19= "Face144.jpg"
/20="Face145.jpg"
</item>

<likert evaluation>
/numpoints = 11
/ anchors = [1="Très déplaisant";11="Très plaisant"]
/position = (50%,50%)
/ stimulusframes = [1 = CSevaluation]
/ anchorwidth=5%
</likert>

<block evaluation1>
/ preinstructions = (introduction, evaluation)
/ trials = [1-20=noreplace(evaluation)]
</block>

<block evaluation2>
/ preinstructions = (evaluation)
/ trials = [1-20=noreplace(evaluation)]
</block>

<picture cs>
/ items = images_cs
/select = current(positif;neutre)
/position = (50%,90%)
/size = (30%,30%)
</picture>

<picture positif>
/ items = images_positif
/select = noreplace
/position = (50%,50%)
/size = (100%,100%)
</picture>

<picture neutre>
/ items = images_neutre
/select = noreplace
/position = (50%,50%)
/size = (100%,100%)
</picture>


<shape rectangle>
/ shape = rectangle
/ color = black
/size = (100%,100%)
</shape>

<item images_positif>
</item>

<item images_neutre>
</item>

<item images_cs>
</item>

<counter setup_positif>
/ items = ("POS1.bmp", "POS2.bmp", "POS3.bmp", "POS4.bmp", "POS5.bmp", "POS6.bmp", "POS7.bmp", "POS8.bmp", "POS9.bmp", "POS10.bmp", "POS11.bmp", "POS12.bmp", "POS13.bmp", "POS14.bmp", "POS15.bmp", "POS16.bmp", "POS17.bmp", "POS18.bmp", "POS19.bmp", "POS20.bmp", "POS21.bmp")
/ select = noreplace
/ selectionrate = trial
</counter>

<counter setup_neutre>
/items = ("NEU1.jpg", "NEU2.jpg", "NEU3.jpg", "NEU4.jpg", "NEU5.jpg", "NEU6.jpg", "NEU7.jpg", "NEU8.jpg", "NEU9.jpg","NEU10.jpg", "NEU11.jpg", "NEU12.jpg", "NEU13.jpg", "NEU14.jpg", "NEU15.jpg", "NEU16.jpg", "NEU17.jpg", "NEU18.jpg", "NEU19.jpg", "NEU20.jpg", "NEU21.jpg")
/ select = noreplace
/ selectionrate = trial
</counter>

<counter setup_cs>
/ items = ("Face1.jpg","Face2.jpg", "Face7.jpg", "Face12.jpg", "Face22.jpg", "Face58.jpg", "Face60.jpg", "Face64.jpg", "face67.jpg", "face75.jpg", "Face77.jpg", "Face89.jpg", "Face93.jpg", "Face99.jpg", "Face107.jpg", "Face130.jpg", "Face138.jpg", "Face139.jpg", "Face144.jpg", "Face145.jpg")
/ select = noreplace
/ selectionrate = trial
</counter>

<trial setup_appariement>
/ ontrialbegin = [item.images_positif.item=counter.setup_positif.selectedvalue]
/ ontrialbegin = [item.images_cs.item=counter.setup_cs.selectedvalue]
/ trialduration = 0
</trial>

<trial test>
/stimulustimes = [1500=rectangle; 1= positif,neutre,cs]
/timeout = 2500
</trial>

<radiobuttons cc1>
/ caption = "Ce visage était il présenté avec une image plaisante ou déplaisante ?"
/ options=("Plaisante","Déplaisante")
/ required = False
/position = (20%,50%)
</radiobuttons>

<surveypage cc>
/ fontstyle = ("Verdana", -16, true, false, false, false, 5, 0)
/ questions = [1=cc1;]
/ stimulusframes = [1=CSevaluation]
</surveypage>

<block conscience>
/ trials=[1-20=noreplace(cc)]
</block>

<page evaluation >
Vous allez maintenant voir plusieurs visages apparaitre à l'écran.
^^Vous devrez noter ces visages sur une échelle de 1 à 11, indiquant si vous les trouvez plus ou moins plaisants ou déplaisants.
^^Ne passez pas trop de temps sur cette tâche, et répondez de la manière la plus spontanée possible.
</page>

<page introduction>
L’étude porte sur des processus de perception de différents stimuli.
^^Elle comprend trois phases. Dans la première, vous devrez évaluer une série de visages.
^^Dans la deuxième, vous verrez diverses photographies apparaitre à l’écran.
^^Elles seront présentées dans un ordre aléatoire (vous n’avez pas à les mémoriser) et dans la dernière, vous évaluerez de nouveau les mêmes visages.
</page>

<page consignes_conditionnement>
Vous allez voir apparaitre plusieurs paires d'images à l'écran, vous n'avez pas a les mémoriser mais vous devez les regarder attentivement.
</page>


<block conditionnement>
/preinstructions = (consignes_conditionnement)
/ trials = [1-12=noreplace(setup_appariement);13-109=noreplace(test)]
</block>

<expt experience>
/ blocks = [1=evaluation1; 2= conditionnement; 3=evaluation2; 4=conscience]
</expt>

I don't see any link giving acccess to any images and the code by itself is not useful. Please provide a complete set of usable materials and please take the time to explain what, exactly, you are unsure how to do. Setups like this have been discussed here before, so I recommend you start with examining those examples: https://www.millisecond.com/forums/Topic2623.aspx

Hello,
Thank you for your reply. Damn, I had to copy it wrong, here's the link: https://fichier.parisnanterre.fr/swq3

What is hard to me to do is that I would like that 12 randomly choose CSs among the 20 are randomly assigne, 8 with positives US (setup positif) and 4 with neutral US (setup neutre). After that, each pair who were created must be displayed on the screen 8 time for 1000 ms after a 1500 ms black screen (rectangle). 

I think that the problem is specifically on that part of the script :

<trial setup_appariement>
/ ontrialbegin = [item.images_positif.item=counter.setup_positif.selectedvalue]
/ ontrialbegin = [item.images_cs.item=counter.setup_cs.selectedvalue]
/ trialduration = 0
</trial>

<trial test>
/stimulustimes = [1500=rectangle; 1= positif,neutre,cs]
/timeout = 2500
</trial>

Is that clear enough ?

Thank you again for helping.

#1: You need two setup trials. One to set up the "positive" pairs, another one to set up the "neutral" pairs. Run the "positive" setup trial 8 times, run the "neutral" setup trial 4 times.
#2: You also need two separate test trials. Again one displaying the positive pairs, another one for displaying the negative pairs. Run those trials in whatever quantitiy you need, e.g. 8x8=64 positive pair trials, 8x4 = 32 neutral test trials.