You can only use your SWUs on DL and sometimes on KLM. Your best bet is to get a subscription to EF, choose the dates your looking for, and then set alerts so EF will alert you when OP opens up on your desired dates. Look on DL.com for all possible routings and then search EF for OP from one of DL hubs instead of RDU, then work backwards to find RP from RDU to the DL hub. Good luck.