A new prop is being introduced in PoserPhysics 2012 SR1, which allows a force to be applied to a ragdoll part or prop at a certain frame. The force can be applied to Moveable, or Keyframed Until Hit figures and props. Keyframed Until Hit figures and props will be converted from Keyframed to Moveable at the frame the force is applied.
Simply parent the PhysicsForce prop to the element you want to apply force to and run the simulation. The force intensity and frame that the force is applied at can be set in the parameters dials of the force prop. If the force prop is parented to a part of a figure which is not converted to a ragdoll (ie. a finger), it has not effect. Set the force prop to be invisible prior to rendering the animation.
Samples are here:
Tutorial is here: