[Simple Q] Showing a Z value on a 2D plot datatip? scatter(X,Y,S,C)

Hi, I am an entry-level, self-taught MatLab user with only VBA as part of my programming backround. I currently have a 2D scatter plot with colored dots as an intensity value :

function altitude(X,Y,Z)

      fh = figure;
      scatter(X,Y,15,Z,'o','fill')
      axis('equal','tight')
      colorbar

      dcm = datacursormode(fh);
      datacursormode on
      set(dcm, 'updatefcn', @showalt)

function output_txt = showalt(obj,event_obj)
% Display the position of the data cursor
% obj          Currently not used (empty)
% event_obj    Handle to event object
% output_txt   Data cursor text string (string or cell array of strings).

pos = get(event_obj,'Position');
output_txt = {['X: ',num2str(pos(1),4)],...
    ['Y: ',num2str(pos(2),4)]};

% If there is a Z-coordinate in the position, display it as well
if length(pos) > 2
    output_txt{end+1} = ['Z: ',num2str(pos(3),4)];
end

The problem is, since it isn't a 3D plot, the 'Z' value isn't showing up on the datatip.

What would be an effective way ,yet simple to understand, to get the according value from the 'Z' row vector and show it on the datatip?

Thanks, Étienne