How to attach custom code after invoice save/modify

Question

Hi to all,
i should solve techically this problem.
I have an invoice document.
After the modify/save of the invoice document, i should start a custom procedure that, line by line, read the invoice document just saved, and save the net value of each position in a custom table.
I cannot simply read the whole net amount of the document, because only positions that fulfill some conditions must be added to the custom table.
On the second step, i should modify that document and create another invoice document whith the positions that doesen't fulfill the conditions above. The same check (and the same code) must be executed on invoice modify also.
Exit, BADI, business transaction events, workflow (that i never use), modify standard trx code (but the customer doesen't want).
These are the methods that i know. I've already searched for exit, BADI and BTE (event 00001030 for example), but nothing of these seems help me on solve the problem, because they all start before the document is saved on the database (so i don't have the document number and the effective data saved).
Any good suggestions/hints/links/solutions etc... will be surely rewarded.
Thx a lot
Andrea

Answer 1

Hi again,
i was quite sure that the problem was solved but .... i was wrong.
The problem is more difficult that what i wrote in the first post.
For this, i need your help/suggestions.
If i create a document 0000001 with VA01 trx, after the document is saved on db,i have to :
- read positions of 0000001 invoice document
- add the net value of some positions in a custom table
- modify some data of some invoice positions of 0000001 invoice document
- save again the document 0000001
Whith the BADI, i can save the net value of the invoice positions in the custom table. The problem is that the BADI code is executed before the commit work. But i think i can solve this problem using a function module ... in update task.
The main problem comes after i saved the net value in the custom table, because i have to modify the invoice document just created.
Before the commit i don't have any values in the db, so how i can modify that values? And with which technique? The BADI doesen't support "PERFORMS" (on commit) and in a function module (in update task) i cannot use instructions like call transaction, call screen, submit etc because they set an implicit commit work --> that means dump during registration.
How i colud solve the problem? Workflow?
Thx a lot again
Andrea