After close examination of the polarizers by B+W, I don't think so...
as far as I can see, these filters do not allow you to change the angle of polarisation.
a dual polaroid foil system has the great advantage of going from single polarisation of light (IE: removing all but one motion vector of the light) to complete darkness, by changing the angle of plarisation between the two foils.
will result in the light being polarised by the first filter. the second filter will not change anything, as the only light passing through it is already polarised in the way it should be.
---> | ---> | ---> c] 0deg 90deg
will result in complete darkness, as the light that has been polarised is now polarised to the direction that the second filter WON'T let through.
anything between 0-90 degrees of rotation will result in an effective grey/polarise filter.
(if it wasn't clear, the "angle" means the difference in rotation of each disc, not a geometrical rotation between the discs. =)
NB: on an interesting scientific sidenote, if you place three polaroid filters in a row, and set them to varying angles, one of them get's "discarded" in the polarisation proces.. I'm not entire sure how this works, and I'll try this soon, but for more information, as Nancy (sharpnack). she told me this oddity exists.