There is nothing to compute easily latencies between events in Brainstorm.
You could probably with a few Matlab command lines, computing the different for the field “times” of the events generated by the process (if you create 2 output events, eg. 10_101 and 1_101).
You can get the events structure in .mat file corresponding to the “Link to raw file”:
https://neuroimage.usc.edu/brainstorm/Tutorials/EventMarkers#On_the_hard_drive