Get one of these.
http://www.logitech.com/index.cfm/products/details/US/EN,CRID=2135,CONTENTID=9340 I have 2 of them. The ergonomics are great, you'd think apple made it. Not Bluetooth, uses USB dongle but it's a minor inconvenience. Batteries last 6 months.
Go to your local big box and try one on. Staples sometimes has a $25 rebate on them.
I use my computer 12 hours a day and I never get cramps and no carpal tunnel.
Scott