I've heard of some people using letro and other AI's in a dermal to locally inhibit estrogen build-up, but if it works or is even possible, I really have no idea.
Also, IMHO, a dermal nolvadex would be kinda redundant as it has a high bioavailability as is, and does a great job at either staving off gyno and/or healing up gyno formations while on cycle.
The only dermal gyno treatment that I've ever read about that had positive results (this is for pre-existing gyno) was andractrim gel (sp?). I've never used myself before, but from what others have said, it does a good job. However to my recollection this is only available through a prescription so....