/*
 * A function to add protection to a sheet so that it's not
 * inadvertently modified
 */
function protectSheet(sheetName) {
  if (typeof(sheetName) == "undefined") {
    var sheet = SpreadsheetApp.getActiveSpreadsheet().getSheets()[0];
  } else {
    var sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName(sheetName);
  }

  var permissions = sheet.getSheetProtection();
  var isProtected = permissions.isProtected();
  if (isProtected) {
    // Browser.msgBox('The sheet ' + sheetName + ' has been protected');
  } else {
    // Browser.msgBox('The permission check shows ' + permissions );
    permissions.addUser('editors@example.com');
    permissions.addUser('joe.boss@example.com');
    permissions.addUser('mary.manager@example.com');
    permissions.setProtected(true);
    sheet.setSheetProtection(permissions);
  }
}