[R-sig-Geo] expanding range in legend in spplot kriging

[Jessica Ruth Hullman]

Hi,

I've been working with gstat and some of the kriging examples for an
experiment, such as using spplot() shown here:
http://casoilresource.lawr.ucdavis.edu/drupal/node/442. I'm using radon
values to create the regions.

What I want to do is change the range of the values in the legend so that
it is larger than the values that are actually shown in the map itself, but
without having to change/add any values to the data itself. It seems that
the legend is always created specific to the map. Is there a way to
manually change the range of values shown in the legend (while adding
cols/cuts)? Do I need to create a map that does have a value that goes as
high as I want, then somehow save the legend from this plot so I can reuse
it on subsequent plots? 

I've looked at the trellis settings to see if I could change it there, but
nothing jumps out as me. Any help on a good strategy would be appreciated,
thanks for your time.