Help with a COUNT / SELECT query

Hi, I have a Bookings application. When a Booking is made it is entered in to the Bookings table. Bookings take place at Areas, held in the Areas table. Each Area has a unique Area_ID held in the Bookings table for each Booking. Each Booking needs to be completed and when done so the Booking_Status for each Booking is updated to '2'. An Area is complete when all Bookings at that Area have been completed. How can I run a query that tells me how many completed Areas there are in the system? Thanks for your help CREATE TABLE WMS_Bookings ( Booking_ID int(11) DEFAULT '' NOT NULL auto_increment, User_ID int(11) DEFAULT '0' NOT NULL , Project_ID int(11) DEFAULT '0' NOT NULL , Area_ID int(11) DEFAULT '0' NOT NULL , Booking_Start_Date datetime DEFAULT '0000-00-00 00:00:00' NOT NULL , Booking_End_Date datetime DEFAULT '0000-00-00 00:00:00' NOT NULL , Booking_Completion_Date date , Booking_Status int(2) DEFAULT '0' NOT NULL , Additional_Notes text , PRIMARY KEY (Booking_ID) ); CREATE TABLE WMS_Area ( Area_ID int(11) DEFAULT '' NOT NULL auto_increment, Area_Name varchar(40) DEFAULT '' NOT NULL , Area_Address varchar(255) DEFAULT '' NOT NULL , Area_Postcode varchar(10) DEFAULT '' NOT NULL , Area_Telephone varchar(15) DEFAULT '' NOT NULL , PRIMARY KEY (Area_ID) );