title: Count the number of times a value is repeated in a column of excel based on a condition
body: <p>There is a list of event types listed in column A, and there is large number of events in column C. Every event in column C has a feature that can have a number of states including "PDA" "tab" "device" and blank. Now I am trying to count the number of times each event type happened but only when the associated feature was "PDA" or blank :
  <img src="https://i.stack.imgur.com/803eV.png" alt="data"></p>
  
  <p>Can you help me please? </p>
  
  <p>Many Thanks, </p>
  
  <p>Hamid</p>