SetTimer.m

function SetTimer()
% this funcrtion is used for set timer to initial value
%
    % elapsed time ( from first click)
    global timeElapsed;
    % time text handler
    global timeControl;
    % a object for timer
    global timerobj;

    % set time to 0 at the beginning
    timeElapsed = 0;
    timeControl = uicontrol('Units', 'normalized', 'Style', 'text');
    set(timeControl, 'string', "000", 'FontSize', 13,'backgroundcol',[1 .4 .4],'FontWeight','bold');
    set(timeControl, 'Position', [0.65,0.87, 0.3, 0.08]);

    % initial timer obj
    timerobj = timer('TimerFcn',@(s,e)UpdateTime(), ...
                                      'ExecutionMode','FixedRate', ...
                                      'Period',1, ...
                                      'StartDelay',1);


end
function UpdateTimeDisplay()
    global timeElapsed;
    global timeControl;

    % Get current time elapsed
    sec = timeElapsed;
    % show curretn time
    secstr = sprintf('%03d',sec);         
    set(timeControl, 'string', secstr, 'FontSize', 13,'backgroundcol',[1 .4 .4],'FontWeight','bold');
    set(timeControl, 'Position', [0.65,0.87, 0.3, 0.08]);

            
end
function UpdateTime()
    global timeElapsed;
    % Increment time counter
    timeElapsed = timeElapsed + 1;

    % Update time display
    if (timeElapsed <= 999)
        UpdateTimeDisplay();
    end
end