title: increment value in real time with mouse wheel in matlab
body: <p>I want to be able to change the value of a number up an down based on the movement of the mouse wheel.  I have an image with a certain part having a different brightness and i want to adjust the brightness with the mouse wheel until i think they are the same.  I thought there was a function called windowscrollwheelfcn but that doesn't seem to exist on matlab 2017. I am also using the pyschtoolbox.  </p>
  
  <p>Unfortunately I am new to this and do not know where to begin. </p>
  
  <pre><code>[winID,winRect] = Screen('OpenWindow', 0, 128);
  HideCursor;
  im = round( 128*( 1 + argyle2 ) );
  im(isnan(im)) = 150;
  Screen('PutImage',winID,im,winRect);
  Screen('Flip',winID);
  </code></pre>