Hi,
you are misunderstanding the function, self means using the referencial of the object you target, so in your case that's not what you want indeed.
1: take the forward camera axis ( z axis) direction, express is in world space ( using TransformDirection action),
2: set the z axis to 0 on that world space vector
3: normalize it
3: use that as the force direction in world space.
Bye,
Jean