Need to push event approvals from SFDC to Marketo - creative solutions?

Hey everyone! I am trying to allow reps to approve/reject leads when they register for a giveaway at an event. Here is what I am trying to achieve:

1. Lead fills out a form, gets added to the SFDC campaign with the campaign status of "Needs Review"

2. Rep reviews the lead and changes the status to approve or reject

3. That status would sync over to Marketo and kick off a series of flow steps based on either approved or rejected

Here is the problem:  Marketo can't be triggered off of the campaign member fields.

I am trying to avoid any additional field setups and need this to be as simple and with as few steps as possible (ya know, because reps ) We also need it to happen instantaneously so a batch wouldn't work. Brainstorming some ideas and would love to hear your thoughts on it!