aw damn hmm, well, you basically need to constrain the vertices. In maya you have something called cluster that you can add to a selection of vertices, and then pulling this cluster handle around, moves the vertices. Look for the equivalent in max.
Maybe you should post more pics of what you hope to achieve. I don't see how this can be done right now, except if the entire object is a multi-segment box with the segment lines running vertically, then you could rotate these vertices with edge constraint on.
I don't think my screenshot could be any clearer to be honest, it was just curiosity and doesn't apply directly to any of my models right now. You seem to get the idea though, but it's not part of a box it's just a flat planar set of faces. The idea is to create an angle from the plane without changing it's length, the…