Classical senario PO creation

Dear Experts,

We are using Classical scenario for creating shopping cart in SRM server and PO in ECC server. While creation of PO we are segregating

the PO based on ECPT and ECPO types. How can i add some more condtions for validating the type of PO i.e ECPT or ECPO.

Kindly guide me how can i add more custom condition while creation of PO.

Thanks & Regards

Arun.K.P