title: Clear Invalid Values from Spreadsheet
body: <p>I'm using Google Spreadsheets for this:</p>
  
  <p>I have a spreadsheet which is basically a 4-week planner. Each day is divided into several slots, which can be assigned to any of our active clients. These cells have validation rules which reject invalid values.</p>
  
  <p>The data that is permitted by the validation rules is sourced from a list on a separate sheet, which filters out clients when their status is changed from 'Active' to 'Cancelled', meaning they can no longer be assigned. The status is changed manually. Once an assigned client changes to 'Cancelled', it becomes an invalid client on the calendar.</p>
  
  <p>Is there a way, using scripts, to find and clear the values of cells containing these invalid values? I've included a screen clipping below. The red corner is the invalid value.</p>
  
  <p>I already have the <code>onEdit</code> trigger set up to run code, this will be calling a function to deal with this specific area.</p>
  
  <p><a href="http://i.stack.imgur.com/kckJb.png" rel="nofollow">screen clipping</a></p>
  
  <p>Any help will be appreciated.</p>