How to create a counter to add and minus?

Im creating a simple counter which helps to add on one button and subtracts when pressing another button. I have done abit of research on this website previously and i found this code. but when i try and change the counter to minus. it doesnt work. Im using MATLAB R2013b GUIDE.

function nurse_Callback(hObject, eventdata, handles)
counter = get(hObject, 'UserData') + 1;
set(hObject, 'UserData', counter);
set(handles.Impt, 'String', sprintf('Number of Nurses currently: %d\n', counter));

Answer 1

[Image Analyst]

Maybe try calling guidata() at the end.

[Kwan Zhao Jie]

For minus should i. btw i got the set(handles.text8,'string','0') in the opening function alr.

counter = get(hObject, 'UserData') - 1;
set(hObject, 'UserData', counter);
set(handles.Impt, 'String', sprintf('Number of Nurses currently: %d\n', counter));
guidata()