WF_COMMIT in Purchase Requisition

[Nieder Martin]

Hello,
 
I'm on work on a worflow for early archiving of purchase requisitions. A
workitem is succesfully created, the transaction me51 is called correctly
and with SAVE a purchase requisition is created. But the link in TOA01 is
missing and the workitem doesn't disappear.
 
I found out that the FM WF_COMMIT (which links the document to the object
and creates the event IMAGE.ASSIGNED) is not called form TA ME51.
 
My question: Do I have to include the FM in the SAP-source (repair) or can I
customize it anywhere?
 
Thank's
Martin