Change Animators motion in Script

Hi Everybody,

Is there a way to do this in script at runtime?

Here's the situation, I have all of my character's animations running perfectly in Animator, but now I need to replace two of them (idle and run), when character is holding a torch. I can add two more animations, but this requires additional lines of code and a lot of changes in Animator. If I could just replace the Motion in script, like in the inspector, which works great, it would save me a lot of work. If anybody knows how to do this, or has any suggestions please reply. Thanks in advance.