[R] How to conctruct an inner grouping for nlme random statement?

[JJ]

Hello.  Im hoping someone can help with a grouping
question related to the "random=" statement within the
nlme function.  How do you specify that some grouping
levels are inner to others?  I tried several things,
given below.

Lets say I have a data frame with five variables,
resp, cov1, ran1, ran2, group1, and group 2.  The
formula is resp~cov1 + ran1 + ran2, where the ran are
random variables.  The data is of length 80, and there
are 4 unique factors in group1 and 20 unique factors
in group2.  These are factors related to ran1 and
ran2, respectively.  

The difficult part is that I want to estimate only 4
random variables for ran1|group1 and the full 20 for
ran2|group2.  I have tried many ways, and I cannot
find a way to do this.  Is there a way?  Can someone
suggest a code snippet?  

First I tried making the data frame a groupedData
object, so that group2 is inner to group1, as it
should be.  Then I used the statement: random =
as.formula(ran1+ran2~1).  But this produced 20
estimates for both ran1 and ran2.

I have also tried it without the data frame as a
groupedData object, using the following:
random = list(group1= c(ran1~1, group2=ran2~1)).  But
this gave only 4 estimates for ran2.  I also tried: 
random = list(c(group1= ran1~1, group2=ran2~1)), but
this just gave a parse error message.

Any suggestions would be greatly appreciated.  Is it
even possible to do what I want to do?  John