Animating RiScreenWindow

[rendermaniac]

Hello,

I would like to animate some values in the RiScreenWindow.

In Pre-World MEL I have

RiScreenWindow -w -1.33 1.33 -h -1 1;

so for instance I would like to animate -h -1 1 to -h 4 6

// To put this in context
I'm interested in the technique of a 2d move over a multipoint
perspective background, while incorporating 3d elements in the
foreground. Its discussed in the section on alternate camera models
pages 447-448
of "Advanced Renderman"

http://books.google.co.uk/books?id=3jM5EZC1rs4C&pg=PA455&lpg=PA455&dq=advanced+renderman+area+camera&source=bl&ots=Tkd9SmMbES&sig=otCLlpLKcZVbfMgI_V23JzEnav0&hl=en&ei=KGopS9XZEIiz4QbQpsShDQ&sa=X&oi=book_result&ct=result&resnum=1&ved=0CAgQ6AEwAA#v=onepage&q=advanced%20renderman%20area%20camera&f=true

Thanks for any help