subcontracting with excise

hi all,

i have a subcontracting scenario like this.

we send the material A to vendor(subcontractor) for job work,then vendor add some material B to material A and send back to us after finishing material will be(a+b).

because vendor paid the excise of material B to goverment,so he want to put execise on material B and send finish material with excise.

In SAP how po will be created for this and what condition type should i use to capture this excise of material B.

pls suggest how to handle this scenario.

regards

sumit