Change gravity point on trigger

Ok, so as the title says, I want to be able to walk on a "pressure plate" that acts like a switch for how the gravity behaves, i.e being able to walk on walls or the roof. I'm very new to scripting and I'm finding it hard to learn these things, so any help is much appreciated. I've seen some similar questions and answers to them have been to just disable the gravity in the standard character controller and making your own gravity. They're not going in to details really., but from what I understand this far is that it's easier to change how the character rotates rather than the enviroment. Thanks!