title: blank instead of zero
body: <pre><code>Duration = isnull(FunctionA(DateA,DateB),'')
  </code></pre>
  
  <p>The Function above calculates number of days and if day is null it displays
  the value 0 instead of blank value</p>
  
  <p>How can I change the above code to so that it shows blank and not 0 for value null?</p>