Updating AVIP table

Hi,

I have a an internal table t_avip which containes the payment advice line item data. Now I want to modify the old data to add some of my owan invoice. What are the fiels that I need to change? Currently I'm changing the document ID(belnr), line item(avspo), and amount(wrbtr & netbtr). Am I doing this right or do I need to change some other fields as well? Note that I want to keep the patment advice header(avik) as the same.

Thanks,

Sarif