title: Periodically refresh IMPORTXML() spreadsheet function
body: <p>I have a large sheet with around 30 <code>importxml</code> functions that obtain data from a website that updates usually twice a day.</p>
  
  <p>I would like to run the <code>importxml</code> function on a timely basis (every 8 hours) for my Google Spreadsheet to save the data in another sheet. The saving already works, however the updating does not!</p>
  
  <p>I read in <a href="https://stackoverflow.com/questions/16100111/google-spreadsheet-row-update">Google Spreadsheet row update</a> that it might run every 2 hours, however I do not believe that this is true, because since I added it to my sheet nothing has changed or updated, when the spreadsheet is NOT opened.</p>
  
  <p>How can I "trigger" the <code>importxml</code> function in my Google Spreadsheet in an easy way, as I have a lot of <code>importxml</code> functions in it?</p>