You can accomplish this by reacting to the selection with a callback and removing the new selection if there are too many.
Create a callback function like this one:
function twoOnly(h,~)
oldValues = get(h,'UserData');
newValues = get(h,'Value');
if numel(newValues) > 2
newValues = oldValues;
end
set(h,'Value',newValues)
set(h,'UserData',newValues)
end
Here's an example of how to use it:
close all;
u = uicontrol( ...
'style','listbox','Max',2,'Position',[10 10 100 100], ...
'String',{'one','two','three','four','five'}, ...
'Callback',@twoOnly)
Note that the 'Max' property with a value of "2" has nothing to do with the limit of two selections. For more information, see the uicontrol reference page.
