can u like use velocity or something?
@kingdom5 is correct. The only way to simulate anti-gravity in Roblox is to use BodyForce and by changing the gravity of the Workspace. You don't have any other choices.
The reason why Velocity would not work is because (from my study) when a player exits the area of Y velocity, gravity in the Workspace kicks in and sends them back down to the baseplate. Just something to know.