Is there a way to easily vary the ISIs within a certain range of durations? I would like to have various visual, auditory, and auditory/visual stimuli presented between random ISIs ranging from 1000 to 1500 ms. So far, all I’ve learned is to build an ISI event with a single ms value. Any way to vary ISI besides creating 501 ISI events with unique values? 
Yes, there is an easier way to do this. Instead of using ISI’s you can create a trial variable. The trial variable can be found under the Experiment menu. Create a trial variable which allows you to enter the values of the ISI, i.e. 1000, 1300, 1500. Once this variable is defined, you will select the variable under the Input tab in your Event Editor. This is where you will see your levels which you have already specified.
When using audio files the only difference is when does the delay start. If Wait for audio to finish playing is enabled, the delay starts when the sound has finished playing. Otherwise, it starts when the sound file starts to play.
I hope this information is helpful.
Yes it was; thanks.