You can try Jos's getkey function. What this function does is read the keystroke a user inputs. Therefore, you can condition the input until you get an enter, something like this:
keypressed = getkey;
while keypressed ~= 13 % 13 is the equivalent to the "enter" key.
disp('Enter was not pressed. Try again.');
keypressed = getkey;
end
disp('Congratulations! Enter was pressed :) .');
