Q on spatial package

Hi, there,
   I would like to compute covariance or variogram matrix on some data
set..
"expcov" or "variogram" function  basically give me a big look up table,
say map covariance value to some lag distance..

I suppose one way to get the covariance matrix is to first generate a fine
grained lookup table, when i need a covariance value for some distance
value, I can look in the big lookup table, find the closet match??
It is sort of a tedious job even if i write some program to do it..
I am wondering is there some built in functionality to acheive that?

Or is there an easier way to generate covariance matrix??

any suggestions is appreciated,
yan