Millisecond Forums

I can't solve a problem and I'll need your help.
I created pairs of images (one negative and one positive or negative) in block conditionnement thanks to trial setup_appariement. But I would like to see these same pairs reversed in a second block)

example :
block 1: image 1 with positive image
             images 2 with negative image

block 2: image 1 with negative image
             image 2 with positive image

Could you give me a lead so I can move forward because I have no idea at the moment....

that's a part of my code : 

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

<block conscience>
/ trials=[1-8=noreplace(cc)]
</block>

<block conditionnement>
/preinstructions = (consignes_conditionnement)
/ trials = [1-8=noreplace(setup_appariement);9-11=noreplace(test)]
</block>

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