title: How to stop a calculation if a cell is filled, while retaining the last value calculated
body: <p>[This is a sample portion of how I'm keeping the record<a href="https://i.stack.imgur.com/SEM3d.png" rel="nofollow noreferrer">][1]</a>I want to keep record of the time passed since a certain entry. Initially I had this as:</p>
  
  <pre><code>=NOW()-[@[Timestamp column(mmm/dd/yyyy h:mm)2]]
  </code></pre>
  
  <p>However, I want the calculation to stop when a cell is filled (indicating a decision made regarding the entry). I managed to come up with this:</p>
  
  <pre><code>=IF(NOT(U5&lt;&gt;""), NOW()-[@[Timestamp column(mmm/dd/yyyy h:mm)2]],"")
  </code></pre>
  
  <p>This leaves me with a blank when the cell is filled. But I want the cell to have a record of how long it took for the decision to be made.</p>
  
  <p>How can I keep the last calculated value?</p>