As I remember, being from UNT, there aren't any rules about this. But it isn't fair to either organization to hold a recruitment office and a NPC office. NPC expects you to represent Panhellenic during that time, while ADPi expects the same. Having a recruitment job would be a conflict of interest. So, it comes down to a choice. Again, i suggest talking to Jennifer McLendon. If you want her email address, I'd be happy to pass it on. Jennifer was my Diamond sister.
Another good one to talk to would be Elizabeth Guithrie. She is an active Alumna that would love to discuss this with you as well. If I remember, she held NPC president also.