How to make an entity sway back and forth?

[Damascus]

I do this in my game:

void SwingLantern2(string &in asTimer)
{
AddPropForce("hanging_lantern_wall_10", 200, 0, 200, "world");
AddTimer(asTimer, 1.5f , "SwingLantern2");
}

Exerts a repeated force on a hanging object. It's kind of obvious by the way it jerks at the exact time the force is applied, but it's the most subtle numbers I could find.