check out
www.samplerobot.comthey make a program for automatically sampling hardware synths, they use a seperate program to automatically find 'seamless' loop points like you are talking about. This is built into the new version, but they are still selling the 'automatic loop finder' seperately.
I have absolutely NO idea if its any good or not, but the sample robot program in its entirety received some glowing comments from either future music, or sound on sound.....forget which, was browsing the computer audio section when I noticed the article
do keep us posted with your findings,
cheers
b0unce