integrate their iCal calendar with appointments+ ... what is the best way to do this?

my clients schedule their business meetings via iPhone on their iCal ... i need to integrate their iCal calendar with appointments+ ... what is the best way to do this?

i need it so the appointments+ appointments show up on their iCal ... and if they schedule a non-appointments+ meeting it will block off or un-allow time from the Appointments+ scheduling calendar.

any help would be greatly appreciated, i've been trying to figure this out for sometime ...

i can import the iCal to the main google calendar, but it comes in under the "OTHER" calendars and there doesn't seem to be a way to sync that with Appointments+