PO Type for Shipment Costing

Dear all,

I have configured the shipment process to run in system as follow:

Sales Order (VA01) --> Delivery (VL01N) --> Shipment (VT01N) > Shipment Cost (VI01) > Post Goods Issue (VL02N) --> Transfer Shipment Cost to FI (VI02) --> Invoice Verification (MIRO) --> Billing (VF01)

The scenario:

The entire process is working correctly and posting to Finance & Acct. Determination is correct. However, During the step of Transferring the Shipment cost to Finance, the Purchase Order (in MM) is generated in background along with the Service Entry Sheet (automatically accepted), which is not a problem.

My question is:

1. How can I determine/configure in the system that during automatic trigger of the PO, it will choose the PO type that I want to use. I am unable to find it in Shipment configurations. Currently by default is taking "NB", which I have found that it is taking the value from the path IMG --> Materials Management --> Purchasing --> Maintain Default Values for Document Type , which for the transaction ME21N (when the system call), it will automatically take NB.

For example I want it to use PO type ZS01, I have to maintain in the above path, but by default when ME21N is executed, it will also take ZS01 in the main screen.

2. If not possible via configuration, any exit possible to use?

Please advise.

Thanks.