Hi,
If its through PM, all will be integrated.
If you dont want this option and follow through the condition type method, then all will be separate process, as of my knowledge. You can insert the material price as a discount condition in PO and post SES with lower value. Create a manual reservation and issue the material against the reservation! You may add the corresponding PO number in any text field in reservation for future reference.
Regards,
AKPT