How to disable some bones in animated character?

Hello to every one,
I am working on an interacting project, and i have an animated character having the idle state. how can i disable the idle animation of hands? i want to put some physics on hands so that they follow the body movements, or drag the hand with mouse while the character is on same position and having its idle animation.

Avatar masks should solve that problem.

Masking allows you to discard some of the animation data within a clip, allowing the clip to animate only parts of the object or character rather than the entire thing.

the problem is that i don’t want to animate the hands. i want to interact with hands while all body animate. for example, think that a character has a tail, and it is animated with character. i want to disable the animation of tail only and drag the tail with mouse while the character animate ( tail acts like rope… with physics), i want to do the same with hands