Statistical information on events

Maybe something like this?

n = 0;
for iFile = 1:length(sFiles)
    DataMat = in_bst_data(sFiles(iFile).FileName);
    iEvt = find(strcmpi({DataMat.F.events.label}, 'your_event_name'))
    n = n + numel(DataMat.F.events(iEvt).times);
end

These are mostly Matlab programming considerations, which is not the primary focus for this forum. Scripting with Brainstorm requires that you have some fluency with Matlab scripting. If you are not confident enough, you might want to start with some tutorials dedicated to basic Matlab programming.