Using parent row in subquery where clause

[FishGuy]

Hopefully you can see from the code what I want to achieve but am currently unsuccesful.

I want to join on to each booking the latest record from from the audit table for that booking, however because the audit table is so big I would like to limit the nested select to only search for the records corresponding to the booking on each join iteration.

Currently though the statement does not recognise b as a table alias.

SELECT * FROM
Bookings as b
INNER JOIN 		
		(SELECT MAX(record_id) as LatestAuditID, bookingnumber 
		FROM audit a 
		WHERE a.bookingnumber=b.booking_number 
		GROUP BY bookingnumber
		) AS aud 
		ON aud.bookingnumber = b.booking_number