CAT2 Configuration for Absence Processing in SAP HR Time Mgt

Hi,

I have a configuration change requirement on CAT2

our client requirement is that they want to book working hours under sending purchase order but the sick leave and other absence types they want to book under directly cost center

but when I am trying to do that , its throwing me error and looking for sending purchase order

Could any one help me with the best solution please..

Thanks,

Sai