Filter a view by Id

Hi Again,
We need a little help filtering a view.
The view is in an appointment table and selects/views the invoice table lines.
I’m trying to filter only the lines associated with the current Appointment Id.
We do not want to manually perform the filter each time there is a new appointment/invoice.
The results of the code used yields the first Id not the last/current in the line table.
Anyone have an easy fix to this code?

(select AppointmentLine)[Appointment.Id]

Thanks