Race timing sheet automation for the August 2020 Funduro

timing.js

function onSelectionChange() {
  var s = SpreadsheetApp.getActiveSheet();
  if( s.getName() == "Sheet1" ) { //checks that we're on Sheet1 or not
    var r = s.getActiveCell();
    if( r.getColumn() == 4) { //checks that the cell being edited is in column A
      if( r.getValue() === '' ) //checks if the adjacent cell is empty or not?
        var today = new Date().getTime();
      r.setValue(today);
    }
    
    if( r.getColumn() == 5 ) { 
      if( r.getValue() === '' ) 
        var today = new Date().getTime();
      r.setValue(today);
    }
    
    if( r.getColumn() == 6 ) { 
      var start = r.offset(0,-2);
      var end = r.offset(0, -1);
      var split = (end.getValue() - start.getValue()) / 1000 ;
      r.setValue(split +"s");
    }
  }
}