Create an online Contract Builder

Hi, i hope someone can help,

I am looking to create an online contract builder for my company’s services.

I would like it spilt it up into 2 or 3 sections, and allow clients to select numerous different services from each sections and for it to calculate the total for all services.

I would like to also limit the number of services they are available to choose in each of the sections i.e. they are only allowed to choose 2 services from section 2 but unlimited from section 2 and 3.

is this possible?
is it a shopping cart I need?
if so can anyone suggest one which offers this service?

Any help with this would be very much appreciated!
Thanks
Mark