plotting two surfaces simultaneously in a single panel

Hi,

I have recently begun using the lattice package, and have been using
the wireframe command to visualise matrices which are model outputs. I
have been trying to plot two surfaces (from two matrices)
simultaneously in one panel, to visualise intersections etc., but
neither my attempts or trawling the net are helping me find how to do
this.

Can someone help? Thanks

Cheers,
Umesh Srinivasan
NCBS-TIFR,
Bangalore, India