Stop callback function in pushbutton if previous pushbuttons not pushed, GUI

Hi, all! I am not good in matlab gui. I have quite simple GUI Listening Test, there are three pushbuttons: first one plays audio files one by one, second and third button saves resulting files. Better explanation: after listening to the audio (first button) subjects need to decide to which category it belongs (category A second button, category B third button). The problem is following: how to stop playing next audio by pushing first button if subject did not pushed 2nd and 3rd buttons?? The ideal scenario is: push 1st button, decide which category (push A or B buttons), then start again from 1st button. There should be error message if subject pushes 1st button without pushing previous 2nd or 3rd buttons. So, how to make this condition?? My code:

% --- Executes on button press in PLAYNEXTAUDIObutton.
function PLAYNEXTAUDIObutton_Callback(hObject, eventdata, handles)
% hObject    handle to PLAYNEXTAUDIObutton(see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
global times_pushed fileCounter

if fileCounter < handles.m             % total number of audio files                                
   handles.FiletoPlay = handles.fileList{handles.perm(fileCounter)};
   [y, Fs]=wavread(handles.FiletoPlay);        
   handles.audio = audioplayer(y,Fs);
   play(handles.audio);
end

if fileCounter == handles.m   
   stop(handles.audio); 
   msgbox('Test is finished. Thank you for your participation!');
   [~,order] = sort(handles.perm);
   handles.result = handles.answer(order);
   handles.result = handles.result';
   finalresults = horzcat(handles.fileList, handles.result);
   xlswrite([char(handles.name) char(handles.age)  '_results.xlsx'], finalresults);
end

fileCounter = fileCounter + 1;
times_pushed = 0;
guidata(hObject,handles);

    % --- Executes on button press in Abutton.
  function Abutton_Callback(hObject, eventdata, handles)
  % hObject    handle to FRONTbutton (see GCBO)
  % eventdata  reserved - to be defined in a future version of MATLAB
  % handles    structure with handles and user data (see GUIDATA)
  global fileCounter 
  handles.answer{fileCounter} = 'categoryA';
  guidata(hObject,handles);

% --- Executes on button press in Bbutton.
function Bbutton_Callback(hObject, eventdata, handles)
% hObject    handle to BACKbutton (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
global fileCounter 
handles.answer{fileCounter} = 'categoryB';
guidata(hObject,handles);

Thank you in advance!

Answer 1

[Walter Roberson]

When a button should not be pushable, set() 'enable', 'off' for it. At the time the state changes so that it becomes meaningful to push it, set() 'enable', 'on' for it.

[Lucky]

thank you, but I dont really understand where to put it, as I understand, in the beginning of categoryA/categoryB button's i need to put 'off', and in the end 'on', is it right? and what is the exact syntax of set() 'enable', 'off' in my situation?

[Walter Roberson]

set(handles.Bbutton, 'enable', 'off')

Do that after the button is created but before control is turned over to the user.

Inside the Abutton callback, when it is time to allow B to be pushed,

set(handles.Bbutton, 'enable', 'on')

[Lucky]

thank you very much! everything works!