Return Beijing Airport - Great Wall

Hi,

I am planning to go to the Great Wall by taking a taxi. I only need to experience few hours of the beautiful world wonder before getting my next flight.
(Private)Tours are offered with a fixed program. Will not fit in my planning.

Can I ask a driver to bring me to the Great Wall and wait for me to return and back to the airport? What do I need to know before going into a cab and how much should I be paying (average) for this service?

Thank you for your time.

Kind Regards,
Holland