title: make image clickable in google spreadsheet
body: <p>I try to make clickable an imported image into Google spreadsheet.
  When I click it to take me to another website.</p>
  
  <p>I was able to:
  - insert the image
  - to 'Assign script' to it
  - that looks like this: </p>
  
  <pre><code>function showMessageBox() {
    Browser.msgBox('You clicked it!');
  }
  </code></pre>
  
  <p>When I click the image the above message comes up. However I need a script that I can assign and opens an outside url when image clicked.</p>
  
  <p>Is there such a script available? </p>