Unfortunately Character Studio does not give the user the ability to create shortcuts to some of the most useful tools it has to offer. This script detects which Biped bones are selected and then mirrors the selection i.e. left arm to right arm. This script supports multiple selections of bones and unlike Character Studio - it can be run on combinations of bipedal and regular bones.
View the Example Movie
NOTE: This script is part of the latest collection of JJTools for 3ds max 7. If you are using a prior version of max - you should download the appropriate script package to ensure full compatibility.