Database Structure And Presentation

I'm trying to design a site for parent conference scheduling.

Usually we have a couple of days appointment time, for example 5/8/2008, and 5/9/2008. and the time usally start at 7:00 and ends at 9:00. one appointment time lasts about 20 minutes.

I would put a page something like this, after parent or student login, 1. they are asked to choose a date, 2.after the date is chosen, show available teacher names, 3, after the teachers are selected, for each teacher, it will show a list of radio buttons for parents to select the time period open, For example: 

 teacher: John smith.
time: 7:00; radio button
        7:20 radio button
        7:40 Booked
...............
        8:40  radio button
       

4, the student choose the available time, and then enter student name, then submit.

I would like to know how to setup the database table and present to the users. Currently for this scheduling part I have tables like teachertable, scheduling table, Appointment table.

Teacher table: teacherID, name, email, course,
Scheduling table: appointD, TeacherID, room, appt date

I think I will prepopulate the two tabels before conference time.

 and after user submit the selection, insert into Appointment table the other fields like scheduling ID, appoint time, and studentname.

The things confuse me, is how can I deal with the appointment time fields, shall I add another table for appt time? should this field be prepopulatd to the table and pull from the table for student to select or something else?

HOw can I do with this: if a teacher not available after 8, how can I excluded the time period for the teacher?

 Thanks