First Element Of Each Sorted Group In Group By Clause

Hi!

I need some help on this:

I have a SQL table with the following structure: ID|ID_GROUP|DATA|TSTAMP

I need to find de column DATA with the highest TSTAMP of each ID_GROUP, so I need to group by ID_GROUP, sorting by TSTAM DESC and take de first element in each group. Any help on how can I do this with CDBCriteria or something similar??

Greats!,

Daniel