title: Excel Multi select options in dropdown
body: <p>In a spreadsheet, if I want to create a list of items for a dropdown for a user to select, is it possible to do a multi-select with checkboxes?</p>
  
  <p>Something like</p>
  
  <pre><code>_ Item A
  _ Item B
  _ Item C
  ...
  _ Item Z
  </code></pre>
  
  <p>and after selection</p>
  
  <pre><code>_ Item A
  X Item B
  ...
  X Item Z
  </code></pre>
  
  <p>and in another cell (or cell in other worksheet), have a comma separated list</p>
  
  <pre><code>B,Z (or 2, 26 for the values)
  </code></pre>