First I'll say you should learn to install a standard rig like TSM2, or AM2008, or "Lite". They have the most functionality for the effort involved.
However, sounds like you need to learn about "IK"
See my "Simplest IK Leg " video for introduction to that:
http://www.brilliantisland.com/am/amtutorials.htm
And an arm is not much different...
http://www.brilliantisland.com/am/amtutorials.htm
Other members have made some fine tuts with more detail on rigging. Hopefully they will join in with links.