Purchase Order Approval Work Center Call

[ND92]

Does anyone know, in the purchase order application, where in the code is the call to send a message to the work center that creates the Requisition Approval message?
Approvals are set up. I'm receiving the message in the work center. But, I cannot find where in the P4310 app or in the MBF, where the message is sent to the work center. I'd like to make some possible changes to the data that is included in the header of the message.

Thank you for your assistance.

 

[ND92]

The call to the work center is within the E1 table trigger for the F4209. A new BLM was created to pass additional information in the description of the order being approved.
I realize that this has been done multiple times in the past, but the call to the work center placement isn't overly apparent.
Note that, more often than not, developer machines are not installed with Visual Studio. The find in files option is very useful, as I'm sure a lot of you know, but in this case, it was absolutely necessary, in order to find that specific piece of code; unless maybe, of course, you're an 'expert' in that functional area.
Thank you.