we need some help. patient came in for physical 99396, but came back two days later for her pap. Can we bill a 99213 with diag. v72.31 or does it have to be at the time of her actual preventive. Could you please help in this matter. I know at the time of the preventive we can code the v72.31, but I am not sure how to code it when they come back two days later.