Hi eric, also since you have Rhino you could try the "MoveFace" command in Rhino to see if it would help you with this kind of stuff right now - I don't think it handles the fully general case like with the sloped sides but it could probably work with 90 degree side wall geometry.
Autodesk Inventor Fusion does this as well. Check out the technology Preview (free for now) or if you have or are going to get AutoCAD 2012 or one of it's variants, it comes included.
This is an interesting preview, but it will only go to the logical limit when you click "OK":
It's definitely fun to play with if a little slow.
Probably you know already, If your solid is something like a wall you can always use the edit frame to stretch it. You have to click the corner first to send the point it scales from to the edge instead of the middle then pull it up.