Link between service request and service contract

Hi All,

We have a scenarieo where we need to allocate specific number of ticket per contract.

And system should be able to keep track of number of tickets raised against particular contract.

If number of tickets are more then allocated one then new service request should not be allowed for contract or in exceptional cases billing will be done at higher rates.

Please let me know how we can incorporate this in SAP CRM.

Thanks,

Naresh