Select Query

Hi All
I've managed to get somewhere with the query below with some help but it has a small problem after rigorous testing I found there is a small glitch e.g. Let’s say if I book from 10:00 to 13:00 and someone tries to book it from 08:00 to 21:00 (all day) IT WILL BOOK, meaning it will over lap. I have tried to sort it but failing miserably, anyone with any thoughts
Thanks
Zed

SELECT b_id, COUNT(*) AS Cnt 
	FROM booking 
	WHERE request_date='$request_date' AND 
	( 
   ($s_time >= s_time AND $s_time < e_time) OR 
   ($e_time > s_time AND $e_time <= e_time) 
	) 
	GROUP BY b_id

Code (markup):

 

Thanks everyone I've managed to sort it, this is what it looks like

SELECT COUNT(*) AS Cnt
FROM booking
WHERE request_date = '$request_date'
AND $e_time > s_time
AND $s_time < e_time