Hi Mirthand,
Disclaimer: This anser is based on an assuption that the first row with a tt.TrialNumber contains the time ('tt.Minutes') where the trial actually started.
Your comment "I think to do this I would want to subtract the last row with the trial and take the Minutes and subtract from the first row with the trial." sounds sensible, and here is a snippet. duration_eachtrial should be what you want.
load tt.mat
allTrials = unique(tt.TrialNumber); % extract all the trials in the mat file
for idx_trial = 1:length(allTrials)
tmp_trialidx=find(tt.TrialNumber==allTrials(idx_trial));
duration_eachtrial(idx_trial) = tt.Minutes(tmp_trialidx(end))-tt.Minutes(tmp_trialidx(1));
end
