Hey Danny,
Any custom order form code needs to be tested on the target order form before being certified as ready to go. I do have some code that I made for a client who needed a very similar thing, and I’ve pasted that code below for you to try it out. It may not be exactly what you need - this tidbit is designed to make an order form into a zero-dollar order form that never asks for payment. It may go beyond what you want, but it’s an easy starting place for someone to tweak to your needs.
https://s3.amazonaws.com/novaksolutions/hosted/javascript/NS_ZeroDollarOrderForm.js