jQuery Grid Plugin - jqGrid

I have a grid like this

    jQuery("#champDetail").jqGrid({
        data: {},
        height: 300,
        width: 800,
        colNames: ['ID', 'Combination No', 'Qty', 'SMT Program', 'SMT Machine', 'Product Date', 'Tracking No'],
        colModel: [{ name: 'ID', width: 50 },
                      { name: 'CombinationNo', width: 120, sortable: false },
                      { name: 'QTY', width: 80, sortable: false, editable: true, editrules: { custom: true, custom_func: QTYCheck} },
                      { name: 'SMTProg', width: 120, sortable: false, editable: true },
                      { name: 'SMTMach', width: 120, sortable: false, editable: true },
                      { name: 'ProductDate', width: 120, sortable: false, editable: true },
                      { name: 'TrackingNo', width: 100, sortable: false, editable: true }
                        ],.................

  onCellSelect: function(rowid, colid) {
            debugger;
            if (colid == 3) {
                var cm = jQuery("#champDetail").getRowData(rowid)
                var temp = cm["QTY"]
                $("#temp").keydown(function() {
                    alert("")
                });
            }

        },...................................

when select a cell,i want to bind a keydown event to the cell ,

but i can't trigger the event.

what is the problem here?