How to update an existing Payables Invoice using Payables Open Import Interface?

 Hi all,

I have a requirement where I need to add a new line to an existing Payables Standard Invoice. Is it possible to update an existing invoice using Payables Open Import Interface and add a new line to that? Also, we need to update the Invoice headers also. Or is there any other procedure or API available to do this task? Your suggestions are welcome. I need to do this as soon as possilbe, so help me to get this done.

Thanks in advance

Gowrishankar