Psychtoolbox: How to end a task using a timer, regardless of trial number?

I need to make a timer that starts counting at the beginning of a multi-phase delay task, and that ends the delay task after a certain period of time has passed, moving on to the next part of the experiment. For now, I'd like to end the task after 2 seconds have passed.

I've made a part of a Stroop task for this delay task that consists of one phase (in my actual code there are 3 phases, but I simplified the task for this question)-- press the 1 key for red, the 2 key for green, and the 3 key for blue. Each phase currently runs for six trials.  (just one set of 6 trials for my one phase for now).

I'd like the task itself (all phases together) to last a period of time, and then terminate at the time I set regardless of the trial number. So if the 2 seconds have passed, the task should end (without closing the screen, just moving on to the next part of the experiment, which isn't shown in the code) even if we are only on phase 1, trial number 3 of 6.

The code below that is commented out (line 23 and 48-50) is my current attempt. I'm not sure where such a loop would go (around the phase for loop, around the trial loop?) The little program should work if pasted into a Matlab editor. Thanks!

CODE:

clear all

close all

KbName('UnifyKeyNames');

%%%%%%%%%%%%%%%%%%%%%%%%%%%%

[window, rect]=Screen('OpenWindow',0);

RED=KbName('1'); GREEN=KbName('2'); BLUE=KbName('3');

    keysOfInterest=zeros(1,256);
  keysOfInterest([RED, GREEN, BLUE])=1;
  KbQueueCreate(-1, keysOfInterest);
    KbQueueStart;

WORDCOLORS = {'red', 'green', 'blue'};

rgbColors = [1000 0 0; 0 1000 0; 0 0 1000];

starttime=Screen('Flip',window);

KbQueueFlush;

% NumSecondsStart = GetSecs;

for phase = 1

    design=repmat([1 2 3], 2, 2)';

    if phase == 1

        designRand=design(randperm(length(design)),:);

        Word=WORDCOLORS(designRand(1:6));

        Color=rgbColors(designRand(:,2),:);

    end

    for trial=1:6

        if phase == 1

        DrawFormattedText(window, Word{trial},  'center'  ,'center', Color(trial,:));

         WaitSecs(rand+.5) 

        starttime=Screen('Flip',window); 

        [pressed, firstPress]=KbQueueCheck; 

        endtime=KbQueueWait();  

        RTtext=sprintf('Response Time =%1.2f secs',endtime-starttime); 

        DrawFormattedText(window,RTtext,'center'  ,'center',[255 0 255]); 

        vbl=Screen('Flip',window); 

        Screen('Flip',window,vbl+1); 

        NumSecondsEnd =GetSecs;

        end
    end
end
% while (NumSecondsEnd-NumSecondsStart) == 1
%                 break;
% end
ListenChar(0); 
ShowCursor(); 
Screen('CloseAll');