title: Adding cell values based on string in next cell
body: <p>Ok, I´ve a row with values and some variable words, ie:</p>
  
  <p>July: 34 - sweaters - 123 - shirts - 12 - trousers - 90 - sweaters</p>
  
  <p>(each "-" means a different cell").</p>
  
  <p>Now, I would need to add all the sweaters and shirts, etc for the month so I would need to sum 34+90 because those are the sweaters, then 123 + the next value for shirts, etc.</p>
  
  <p>How should I do that?</p>
  
  <p>Thanks for your help!</p>