Substitution for Process Order Activity Confirmation

Hi experts,

Need urgent help on substitution for process order/activity confirmation

Clients wants to update process order number in the accounting document of Activity Confirmation. This is an inter plant transaction. One Plant gets some work done in a plant located in a different country. So the second plant charge the first plant for the work done with a mark up (x%)

While posting the activity confirmation One a/c document each posted in the two company codes. Now, after activating the Process Order - in the real time integration for CO FI, I can see the process order number updated in the debit (exp) line item of the sending plant (say 1234). System creates accounting document first in the recieving palnt (say 5678) associated company code. In that, the process order is not updated in any of the lines which is still fine for me.

I need the process order number that is updated in the Debit (PK-40) line of the sending plant associated company code, to be updated in the Reference Field. I am primarily looking at a substitution.

I have created a substitution in Financial Accounting > Line Item. (In Header level I can select only BUKRS. In Line Item level I can select both BUKRS and GL Account) I have selected prerequisite "When BKPF-BUKRS = <co.code of 1234 plant> and BSEG-BSCHL = '40 and BSEG-HKONT<xxzzxxzz> (this GL is only meant for this posting), then substitute XBLNR by BSEG-AUFNR)

In my testing this is not working. Could you please help urgently?

(When I set the prerequisite wth BUKRS and GL A/c, this was not working)

Thanks in advance!