updateUnattendingRows

updateUnattendingRows.js

function updateUnattendingRows() {
  var attendingValues = sheet.getRange(startRow,4,rowRange,1).getValues();
  var color = "lightgrey"
  
  for (var i = 0; i < attendingValues.length; i++) {
    var rr = sheet.getRange("A"+(i+startRow)+":I"+(i+startRow))

    if(attendingValues[i][0] === false && rr.getBackground() != color) {
      rr.setBackground(color);
    } else {
      rr.setBackground("");
    }
  }
}