Database Validation – MS Access

Hi there, im building a database in access at the moment, im having difficulty with validation rules (they are mandatory for this DB) ive made an “appointment” table, within it there is a field called “Appointment_Date/Time”, what i need is a rule that will allow a date from in 9am and 12pm, and 1pm to 4pm, anything outside those times have to return a message. Can anyone please give me some tips? ive had quiet a bit of trouble trying to find help with this, thanks in advance