jQuery Grid Plugin - jqGrid

My current requirement is to always sort the first column in the grid, so if a column is dragged into the first position of the grid it should be sorted. How do I handle the drag and drop event to know when a column has been dragged to the first position in the grid? Is there an onDragCompleted event that can be handled? I have already tried the following with no success:

jQuery("#list").jqGrid('gridDnD', {
                onstop: sortColumn()
            });