LPN to RN

I'm hoping someone can give me advice on this. I have researched on the internet with no definitive answer. I am currently employed as an LPN and recently became an RN. my current job is changing my status to RN. What is the proper way to list this on a resume? Do I list my LPN time span and RN time span separately? I asked at the local work-source office and they said you always list your highest level job with any one specific employer, but I don't want it to seem misleading that for part of my employment time I was an LPN. Help!