Compulsory booking of two services

First of all it's a great plugin... It worked out of box for my application. But I am stuck at one last issue... look at this link >> wadrivertesting.com/book-appointment/retest/seattle ...

there are two services "driving test" and "written test". What I want is, it should be compulsorily for a user to book both. not just one. It should throw warning to user if only one service is in cart during checkout. Or two different timeslot selection in one service it self would also do. also there will be other services which do not follow this... Is there any hack or suggestion, so that I can make it work?

Hi Jayesh,
It seems impossible to compulsory customers to purchase services in OS Services Booking. Because services in OSB don't have any relation. I think you can add the message at the service details to warn customers or you can combine 2 services to one. It means when user purchase one time slot, they will have 2 test services are "Driving test" and "written test"
Thanks
Dam

can I somehow have two different timeslots each for "written test" and "driving test" in single service... I am ready to do any php or javascript hack if it is at all possible. I need direction from you. from where to start?