How to limit the number of words allowed in a post title

It looks like there have been quite a few similar questions to this over time, but none answer my specific question, or any that do provide code which results in errors when I insert it as described.

What I need is a way to limit the number of words in a post. Simple as that. Not to limit the number visible once published, not limiting characters, but actual words. I want to limit to four words, and if possible have it exactly four, no more or less, with an error message if a post is submitted without 4 words.

I've found quite a few bits of code online but either the coder was vague in where to insert the code in the multitude of files within Wordpress or when I inserted where advised it crashed my site.

Please help? Losing the will to live here!

Thanks in advance,

Tom.