3ds max animation Problem; Move root bone of animated model?

Hi, I’m making an NPC and can’t make proper walking animations without the animation moving forward about 120 units. I can’t make this animation because the model is already animated and replacing the root bone’s animation will make the model move awkwardly. The tutorial here:Locking NPC Animations Suggests that I delete all but the first frame, but that won’t work. So basically I need a way to animate this bone while keeping the original animation in tact. Is there any way to do this in 3ds max?