title: Calculate SUM based on date
body: <p>This is driving me nuts and I don't know what I'm doing wrong.</p>
  
  <p>I have an excel table where my turnover is in with the date of incoming invoices. The date is in format <code>ddmmjjj</code> and is in column C.</p>
  
  <p>I want to calculate my turnover on my dashboard. The total turnover is in column G.</p>
  
  <p>The formula I use is:</p>
  
  <pre><code>=SUM(IF(MONTH(Sheet1!C:C)=2;Sheet!G:G;))
  </code></pre>
  
  <p>But this formula keeps giving me the total turnover... What am I doing wrong?</p>