Time Slot Booking, Time rather than minutes

When a Client books an a Appointment, i would like the conformation section to say:

Date and time: May 17, 2013 6:00 pm - 7pm

Rather than:
Date and time: May 17, 2013 6:00 pm
Lasts (approx): 60 minutes

As i will be traveling to clients homes, i would like an hour window as to when i can arrive.

so if they book 6pm-7pm i would like it to match that in the conformation and hide/disable the "Lasts 60 minutes" Section.

is this possible? many thanks