jQuery Grid Plugin - jqGrid

Is there an easy way to implement this? Because I want to return row data and update rows if they exists or add them if they don't. But updateGridRows returns only true or false, so I don't know which row ids where not update (which means ids that need to be added) and addRowData does not check for duplicate row ids (so I could run update and then add with the same data). It seems an overkill to have two different ajax calls one that returns rows that need update and one that returns rows to be added.

Thank you very much.