I keep taking my cat to the vet

I have a cat that has a scab that keeps getting bigger and I think it ringworm but the vet says no!!  can I try a antifungal cream I bought at the store on her or will it hurt her?

[Savas]

Ringworm is treatable with an athlete's foot cream like Lotrimon AF or a generic equivelent.  Cover the area thoroughly twice a day until it clears.  However, what did the vet say it is?  Lots of things can cause scabbing like that on cats.  Ringworm is the first one I think of too, but it certainly isn't the only thing.  

The cream shouldn't hurt the cat.  But if there is an actual wound or open, bleeding area, I might be concerned about getting the medication in the cat's bloodstream.  Didn't the vet give you something to treat the problem?