Some implementation can be done with subgrid module where the main columns are the summary (data is all form server) and the subgrid has a detail lines.

I plan to include in the next releases (not in the upcomming) treegrid which will do that very easy

Regards
Tony

Look here
http://www.trirand.com/blog/index.php?pagename=forum&rs_discuss_where=topic&rs_discuss_forum=discussion&rs_discuss_topic=105&recent=479

Download the jqGrid32-test
and use afterInsertRow
I supposse that the id of summary row is something like
sum1,sum2….

afterInsertRow:function(rowid)
{
var sumrow = rowid.toLowerCase().substr(3)
if ( sumrow == “sum”)
{
jQuery(“#”+rowid,”the_id_of_the_grid”).addClass(“myclass”);
}
}

Regards
Tony