SQL 2008 database update

Question

We have a table in a hotel management system, the table is called RoomAvailability, the fields are roomID int, roomDate DateTime, Available bit.... the roomDate field is populated with every single day of the year, as a client is booked the relevant days are supposed to be marked unavailable.... could some one please help us with the SQL statement to update this table because its been a long time now that we're stuck on this