def count_words_between(start, stop, words):
    """ Count the number of words between the start and stop word """
    word_list = words.lower().split(' ')
    count = 0
    counting = False
    for word in word_list:
        if word == stop.lower():
            return count
        if counting:
            count += 1
        if word == start.lower():
            counting = True
    return "One of the start or stop words was not in the sentence."