BOR method for transaction FV60 - FI invoice creation

Question

All,
I want to create a workflow step to create an incoming FI invoice.
This is done using transaction FV60. Now, I call this using BOR object BKPF method CREATE.
But this is an async method which only triggers event CREATED from object FIPP. A different object.
I am able to catch the event for the termination of the task, but how do I know for sure this is the correct FIPP belonging by my just-entered FV60?
Or is there another way to call FV60 in a workflow? It has to be one of many steps.
Situation:
The trigger for the workflow is an incoming image from the scanner.
Workflowstep1: display image and determine type of invoice ( MM / FI ) and send it to person 2.
In case of FI:
Workflowstep2: FV60 for creation invoice and send it to person 3
Workflowstep3: FIPP-CHANGE for entering additional data and send it to person 4
Workflowstep4: FIPP-CHANGE for checks and approval,
In case of MM:
Workflowstep2: MIRO for creation invoice and send it to person 3
Workflowstep3: BUS2081-EDIT for entering additional data and send it to person 4
Workflowstep4: BUS2081-EDIT for checks and approval
End step: booking of the invoice.

Answer 1

The process I used in my project was is this:
the user receives the image -> creates an invoice -> links the image to the invoice
I created an event from the change documents of the dms object, when the DMS object was changed I used a function module as the receiver of the event (DRAW.Changed) and in it checked if the dms object was linked to an invoice. if so I raised another event to close the task (DRAW.LinkedToInvoice).
Now the terminating event will be on the DMS document and you should have it's key in the beginning of the task.
The link to the document was done by classification of the DMS document (incoive number & year) but it can also be done by creating a dms object (there isn't a standard one).