PO Output Determination is not working while releasing PO via Workflow

Hi all,

We are trying to determine Output Type for Purchase Order while releasing it. Actually We have made a Routine where we are building our logic to set Output type based on Vendor's Communication method. Its working fine for everything but problem is while trying to release PO via Workflow its not working. We put break-point inside the routine but it did not stop even from the BOR method its  also not working. Please help to understand what I'm missing .

Thanks in advance,

Biswajit