tricky really, as props own sampler is good at such things, and other things like kontakt
how about try using
http://vemberaudio.se/shortcircuit.php and see how you get on, as it support REX / RX2, but as I use Kontakt I don't use it.
there's always the issue of the pitch / length of the slices changing as well. I use recycle and thats the only real way to edit recycle files, apart from bouncing the audio out again and doing the modifications yourself. Although not everything can be done in recycle (which I find a pity).