Sollthar, how complex is the motion? I've used a technique called Rotoscoping (although I think that term is used way to much...)
1. Shoot your actors in front and profile, (It worked for me just using the profile footage)
2. Take the footage into your 3D software and throw it in the background.
3. Match your CG charater to the same angle and stance as in the footage.
4. Identify keyframes for your movement.
5. Key your CG character at those keyframes.
You now have some movement that, while it isn't as accurate as motion capture, yeilds alot more realistic results, and contains many of the nuances<sp> that you would get in motion capture that animators tend not to throw in to their work.
The first time I went through this I had many people convinced the movement I had was MoCap. So for your average person, this works effectivly if done correctly.