Arduino support package send two value at the same time to different port

I need to trigger EEG and fMRI at the same time by a visual stimulation I wrote in matlab. I can use the arduino support package to trigger trigger to the EEG system sychronzing the visual stimuli and EEG recording, but I also need to trigger the fMRI scanner. I am thinking connect two arduino boards to my computer via different ports and send two triggers to two ports respectively and simultaneously. How can I do that?

I wrote the code below to synch EEG and visuals stim.

P.S. the visual stim were writen using the VisualStimulus toolbox version 1.0 by Michael Beyeler.

a = arduino('com3','uno'); % Create an adrduino object

f = figure; f.WindowState = 'maximized'; % max the figure window

for deg = (0:7)*45

blank = GratingStim([300 500],'k',20,deg,[1,1],0.1);% generate a blank pic

blank.plot % plot the blank picture

grating=GratingStim([300 500],'k',20,deg); % generate stimuli

writeDigitalPin(a,'D4',1) % write to EEG to start recording

grating.plot % plot the stimuli

writeDigitalPin(a,'D4',0) % write to EEG to end recording

end

clear a % delete the arduino object