Format line according to group

[Miguel]

Hi,

I would like to ask a simple question: Is it possible to have
gnus-group-line-format set to all the groups and, for specif groups, change it?
 For example, I have this variable set with "%m%M%S%5y/%R: %(%g%)\n" but would
like to have, for the groups where I keep the sent mails (which are kept in
groups named like "nnfolder+archive:mail.sent-2004-12"), with a different 
format.

I tried (without success) to use the gnus-parameters to do this. Is this
feasible? Could anyone provide me with an example?

Thanks,