final Ref ref = getRefs().iterator().next();
final Worksheet sheet = BookHelper.getSheet(_sheet, ref.getOwnerSheet());
final Set<Ref> all = new HashSet<Ref>();
final boolean oldProtected = sheet.getProtect();
if (oldProtected && password == null) {
sheet.protectSheet(null);
all.add(ref);
} else if (oldProtected == false && password != null) {
sheet.protectSheet(password);
all.add(ref);
}