There are various ways and choice depends upon what kind of update you want to make in auto grand summary row:
1) If it's an aggregate, then consider to use inbuilt aggregates or create your own aggregate by extending pq.aggregate and use it in column.summary.type
2) If it's formatting or textual change, use rowInit to make a change:
rowInit: function(ui){
var rd = ui.rowData;
if( rd.pq_grandsummary ){
rd.ContactName = "Hello World";//make your change here.
}
},
3) use of column.render callback to make a change similar to rowInit callback.
