Millisecond Forums

Hi everyone,
I've been successfully gathering data using a Stroop task where both congruent and incongruent items were displayed at a 50% ratio. To do so, I've created a block for congruent items, another for incongruent ones and used the "noreplace" function and setting the number of trials to the desired number of trials. I'd now like to do the same but with a different ratio of presentation (like 30% congruent and 70% incongruent for instance). I've been thinking of creating two lists of items and to display them in sequence but doing this would get rid of the random sequence and I'd like that to remain. In sum, I'd like to be able to only change the frequence of the items' display but to present them randomly.

Is there a quick way to do that ?

Thanks or any input,
Best,
Vince.