Trials with same events except one

Hi There,

I am designing a task where participants have to watch a video and then answer 3 questions (3 events). However 20% of these videos have a 4th question that must be asked. The list is randomized (externally from Superlab) and therefore the stimuli requiring the 4th question do not appear in a regular pattern. The stimuli are entered manually in a stimulus list. Is it possible to have a trial run such that for 80% of the trials only 3 questions are asked but for the specified 20% I can use a tag to prompt running the additional event? Can this be accomplished using tags?

For those 20% of trials that get a 4th question, is that question the same for those trials? or does each trial get a specific matching question?