How to Set NAST-AKTIV while creating Invoice VF01/VF02/VF03

Hello Gurus,

Below is the requirement in our project.

Current procedure :

Each time after creating Invoice , Output Type ZXXX ( Medium 6 -EDI ) will trigger in yellow with VSZTP = 1(Send with periodically scheduled job).

Then we are processing this output Type with RSNAST00 and IDoc is generated once output Type is processed ( now output type is green mode).

Now , Requirement is like Output Type should processed if and only if Invoice is Approved i.e Posting Status is 'C'.

I found function exit for RSNAST00.

Enhancement : VN000001 Customer exits in output determination

EXIT_SAPLV61B_001 WFMC: Find Fax Number

EXIT_SAPLV61B_002 WFMC: Set Print Parameters

But none of this is related to medium 6 EDI/IDOC.

I did some R&D and found out that if NAST-AKTIV = 'X' then output type will not be processed by RSNAST00.

So I am thinking to write below code in some user exit.

IF Posting Status EQ 'C'.

NAST-AKTIV = ' '.

ELSE.

NAST-AKTIV = 'X'.

ENDIF.

Problem is I am not able to find userexit where I can modify NAST structure as it is non-modifiable in user exit.

Can someone help in where I need to write the code or is there any other way to achieve this requirement.

Thanks in advance.

Regards,

Mayur