Animatable envelopes Max 2010

Im currently doing some animation but i have also got to do some stuff with the envelopes. Im using 3ds max 2010, a biped rig and a Skin modifier. I have done all the animation and it looks solid but just one pose looks crap due to the envelopes, i was wondering if there is a way to animate the weights so that i can keep it at say 1.0 on frame 0, then at frame 50 make it effect by 0.5. Along those lines any help would be cool.
Cigaro

there is a “Animatable Envelopes” toggle in Skin’s advanced section. If you activate it , you are able to animate the envelope shapes. Not sure if you can animate the weight of specific envelopes…