Updating target for multiple constraints

In blender 2.68 I have two armatures in two different layers.
Armature A was made in the scene and armature B is an imported BVH file.

In pose mode I created a “copy transform” constraint for each bone in armature A. The target is set to armature B, and bone is set to the required bone in armature B.

I have many other BVH files for different animations and they all conform to the same structure and bone names.

If I load one of these into blender on an empty layer, and want to get this animation onto armature A, I have to go bone by bone in armature A and update the constraint target (the bone name doesn’t need changing thankfully!).

Is there a way to do this in one operation?

Many thanks