Copy/paste part of an armature

Is there a way that I can select only part of an armature on a given keyframe, and copy/paste that part onto another keyframe without affecting the parts that weren't selected?

For example, copy the position of the torso, and place that onto a keyframe where the legs and torso have moved, adjusting the position of the torso, but not the legs?

I'm using an armature attached to graphic symbols.