jQuery Grid Plugin - jqGrid

I have many uses for this.

(1) I need to make the sort index persist in the POST data so that the grid would always be sorted even after any operation. I put this code

$(grid).bind('beforeRequest', function() {
                var sidx = $(gridElem).getPostDataItem('sidx');
                $(gridElem).setPostDataItem('sidx', sidx);
});

and including sidx as an extraparam in editRow, but sidx is still removed from the POST data after add/edit/deleting a row.

(2) I need to modify inputs of the edit operation before executing the request.

Basically, I need to know how to make the POST data persistent even after CRUD operations.