Inverting a BodyVelocity's force on the Y axis?

I was making a spaceship, but I encountered a problem. It works fine on the X and Z axis, but when the VehicleSeat is tilted downwards the seat goes up, and vice versa. Below is the part of the script which handles a throttle of 1.

if script.Parent.Throttle == 1 then

    if value1 < maxspeed then value1 = value1 + script.Parent.Settings.Acceleration.Value end

        script.Parent.Driving.Value = true

        script.Parent.BodyVelocity.Velocity = script.Parent.CFrame.lookVector*value1

        script.Parent.Left.Value = false

        script.Parent.Right.Value = false
end

How do I invert the force on the Y axis to fix the above problem?