title: Excel formula using 'Filename' updating in other worksheets
body: <p>I have my tabs named as month-end dates, and I am constantly forgetting to update the date cell (which becomes important when I have to print).  So I figured I would use the <code>'Filename'</code> property, the <strong>Left/Right/Mid function</strong>, and the Date function to automatically set the date cell.  This is what I came up with:</p>
  
  <pre><code>=DATE(RIGHT(RIGHT(CELL("filename"),8),4),LEFT(RIGHT(CELL("filename"),8),2),MID(RIGHT(CELL("filename"),8),3,2))
  </code></pre>
  
  <p>The internal "<strong>RIGHT</strong>" grabs the last 8 chars of the filename (the worksheet title), then the external substring functions portion it out so that it can be used as parameters for the "<strong>DATE</strong>" function.  And this works fine.  The problem comes when I try to copy this over from worksheet to worksheet.</p>
  
  <p>First, I have made sure that my tabs are NOT grouped.</p>
  
  <p>But still, whenever I calculate ONE of the cells containing the filename property, it updates ALL of the worksheets to have the date of the last sheet used to calculate.</p>
  
  <p><strong>I.E.</strong> I calculate the date cell in sheet <strong>"05312013"</strong> and it changes all months' date cell to <strong>"05/31/2013"</strong> instead of JUST that one sheet as intended.</p>
  
  <p>What is happening and how do I fix it?</p>