Callback in push button doesn't work

Hey I have a simple if function that I want to start with a GUI pushbutton. It only works when I put uiwait before the if (local function) and the uiresume in in the callback function. In debug mode it works without it. How can I preclude using uiwait?

Matlab function

run GUI.m
global start
while true
uiwait;
if start
...
end
end

My GUI pushbutton callback function:

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

 global start
 start=true;
 uiresume;

[Ingrid]

your question is not really clear as the code you past is not a function. Could you give a bit more information and code i.e. the actual pushbutton callback and explain what you are trying to achieve

[mat]

I updated the code

Answer 1

[mat]

Seems like drawnow did the trick.

Answer 2

[Walter Roberson]

If you have code that needs to delay until a button is pushed, then you should put the code itself (or a call to it) into the callback of the pushbutton.

[mat]

code should still be running in a while loop, I don't want to have delay. But atm the if function only works when using uiwait.