[R] Levelplot + Mosaic Plot hybrid?

[Kitty Lee]

Hi. I have built a levelplot with 3 variables, X, Y, and Z where X and Y are the two axes and Z represents the intensity (i.e. Z~X*Y). 

Now I want to adjust the size of the grid (like a mosaic plot) where the size of each grid is weighted by a variable, W.

Just wonder how can I do that with levelplot? 

I tried exploring mosaic plot. How can I manipulate the "col" option to make it represent my Z values?

Any help would be really appreciated. :-)

K.