title: Count number of blank cells in row between last cell and next non-blank cell
body: <p>Is it possible (with a formula preferably) to count the number of blank cells in row, where the counting starts at a given column and counts going backward (e.g. right to left) the number of blank cells until a non-blank cell is found?  In the example below, the counting begins at Column H and proceeds leftward.  Using <code>COUNTA</code> or <code>COUNTIF</code> seem like reasonable tools to use, but I am unsure on how to terminate the counting once a non-blank cell is found.</p>
  
  <p><img src="https://i.stack.imgur.com/B0sUp.jpg" alt="excel screen shot count blank cells until non-blank"></p>