How do I prevent manufacturing a prototype?

I'm not sure if this belongs in the manufacturing forum or the distribution forum.  My apologies if it is in the wrong forum.

I have a situation where we are designing products and want to prevent manufacturing from entering and processing WO's for those items until they pass through the Pre Production Approval Process (PPAP). Is there a way in vanilla JDE to prevent this from happening other than having a separate B/P (and all the associated maintenance) for engineering? The ECO process does not appear to do what we want as once the items are entered, they are "live".