Óscar - if you want to disable the callback then you should just "remove" it, and then "add" it back when it is required. Given the name of your call back, it seems that areas(i) could be a handle to a graphics object (image). This handle, and all that which is in areas could be saved to the handles structure in the OpeningFcn as
handles.areas = areas;
guidata(hObject,handles);
Then in whatever callback that fires to decide that the ImageClickCallback should be removed from areas(i), you would do something like
% disable the callback
set(handles.areas(i), 'ButtonDownFcn',[]);
To re-enable this callback, you would then just do the following (in whichever callback that fires to decide that ImageClickCallback is needed)
% enable the callback
set(handles.areas(i), 'ButtonDownFcn', @ImageClickCallback);
