plot output of timer function

Hi everyone,

I am pretty new in Matlab and it's the first time I use the timer function. My purpose is to plot a variable that is the output of the timer callback function. I wrote this

   f=start_timer;
   b=f();
   t=1:rows(b);
   plot(t',b);
   linkdata on
   end

Where start_timer is a nested function as below:

function [display_fn] =  start_timer

MyTimer = timer('TimerFcn', @RND, 'Period',10, 'ExecutionMode', 'fixedRate');
display_fn = @TimerDisplay;
start(MyTimer);
a=0;
  function RND(g, h)
      a=random('Normal',0,1,10,1);
  end

    function b = TimerDisplay
     b = a;
    end

end

end

When I run the code the plot with the initial value appears but it never updates, any help or suggestion?

Thank you

Gaia