title: SUM Excel column if row not blank, otherwise take value from left cell
body: <p>I have a table:</p>
  
  <pre>
  Job name        Cost    Assessment
  ----------------------------------
  Job 1            400    200
  Job 2            100    30
  Job 3            80     
  Job 4            100    10
  Job 5            20    
  Job 6            340        
  ----------------------------------
  SUM              1040   680
  </pre>
  
  <p>I need some formula, that SUM Assessment column, but if cell is empty, take value from left cell.</p>