Get Current Entry ID in POST Data in Extension?

When a form submits, specifically I am using FreeForm Pro for my forms, is there a way without putting a hidden input with a value of {entry_id} in it to pass and get the current entry_id in the POST data?

I am building an extension with the FreeForm Pro extension hooks, and it would be nice if there was an object that held the current entry id somewhere but I am not seeing it.

Thanks in advance!