oracle concurrent program related

[fasi.hrms]

Excel report to be automated from Oracle ERP system by a concurrent job on a 1st of each calendar month with date parameters of 15th to 31st of previous calendar month



Excel report to be automated from Oracle ERP system by a concurrent job on a 15th of each calendar month with date parameters of 1st to 14th of current calendar month

please tell me how to define above CP parameter with default values dates

Thanks.....