How to measure time with Matlab while led diodes is on using Arduino? -

i need measure time while led diodes on each 1 matlab guide. in arduino code sending data matlab if diodes on:

if(digitalread(ledc1)==high) { serial.println("a"); }

if(digitalread(ledc2)==high) { serial.println("b"); }

with matlab code, works if 1 diode on, not working if 2 diodes on in same time , not measure each one. how measure both diodes?

matlab code:

function pushbutton1_callback(hobject, eventdata, handles)

s=serial('com7','baudrate',9600);

fopen(s);

try

 while true     pause(1);  

a = fscanf(s,'%s');

b = fscanf(s,'%s');

if strcmp(a,'a')==0 % frist led dioda

    tic; 

end

    seconds1=toc; 

elapsedtime1 = fix(mod(seconds1, [0, 3600, 60]) ./ [3600, 60, 1]);

set(handles.text8,'string',elapsedtime1);

if strcmp(b,'b')==0 % second led dioda

    tic; 

end

    seconds2=toc; 

elapsedtime2 = fix(mod(seconds2, [0, 3600, 60]) ./ [3600, 60, 1]);

set(handles.text9,'string',elapsedtime2);

end

end

catch err

fclose(s);

clear   return; 

end