Order Hold code entered manually after initial order entry

We have the situation where we are using C1 for credit limit holds, CX as a Credit or A/R review hold in the Billing Instructions, and then PN as an admin hold for the Customer Service group.  When Customer Service places the order on PN hold at order entry in the header of the order, the order holds applied are only the C1 and PN.  The CX hold does not get assigned to the order.  Is there a way to enter the order and then add the PN hold to the order?  We are using E1 9.0 and the P42101