title: Change OptionMenu based on what is selected in another OptionMenu
body: <p>I am currently trying to make two <code>OptionMenu</code>s, where the second will be updated dynamically based on what is selected in the first <code>OptionMenu</code>.</p>
  
  <p>For example, I would like to make <code>OptionMenu_A</code> with list </p>
  
  <pre><code>[North America, Europe, Asia]
  </code></pre>
  
  <ul>
  <li>If <code>Asia</code> is selected, then <code>OptionMenu_B</code> will change to something like <code>[Japan, China, Malasia]</code>.</li>
  <li>If <code>Europe</code> is selected, then it will change to <code>[Germany, France, Switzerland]</code> for example.</li>
  </ul>
  
  <p>I am able to make two <code>OptionMenu</code>s but can't get <code>OptionMenu_B</code> to update based on <code>OptionMenu_A</code>'s status. </p>
  
  <p>Would anybody be kind enough to show if such thing is possible? </p>