>I am building schedule table for a an appointment form in a software to dentist
>
>Please take a look below and give me your opinions if possible
>about which seems best choice
>
>1- Specify a fixed time to every patient consult. 30 min.
>(seems easier)

Yes, it's easier and it's usually the way manual appointment tracking works. You've to check with your customer if he wants your system to work the same way.

>2- Let a free space to the doctor to set the time to each patient
>(seems more complex)

See above.

>Also, is there friendly a calendar activeX wich I can associate to a table ?

Check http://www.dbi-tech.com. They have VFP friendly controls including Appointment Scheduling http://www.dbi-tech.com/ProductPage_StudioControlsCOM.aspx.
They also offer some free ActiveX controls for owners of VFP9SP2 and Sedna at http://www.dbi-tech.com/VisualFoxProSedna.aspx