Integration with CustomPress: Form submitting Posts/Pages

I need a form which will:

1. Submit information an create a new post (without user authentication)
2. Submit that same information to an outside url (an outside payment form)
3. On post back, update a field in the new post saying it has been "processed"

I cannot use a different process due to business requirements. I am a developer.

Any recommended plugins with CustomPress to achieve this workflow?