To Transfer the quota values on beginning of the year/Hiring date of an employee

Hi SAP'ers,

Please help me to configure the following scenario for my clientrequirement,

We have Annual Quota leave of 20 days for all the employees in the enterprise, but i need to entitle all the 20 days in the beginning of the year i.e 01-jan-XXXX. And if the employee joining after 01-Jan-XXXX, then pro-rate calculation should be entitled.

Please help me, whether this can be done through configuration or through Schema by defining a new rule in the previous day processing.

Thanks in Advance. Kindly help me to resolve it as soon as,

Thanks

Prabhu