You can use a client side code (I didn't test it).
ClientEvents->ExtEvents->(added event):
function added(sender, container, index, eOpts)
{
sender.store.setGrouper({
groupFn: function (item) {
return item.get('2')+ ' - '+ item.get('11');
},
sortProperty: '2'
});
}
Remember that Unigui uses the column index as the field name.