jqGrid - dynamic Enable/Disable column editable

I did it in beforeSelectRow event of jqGrid (cell edit mode):

beforeSelectRow: function(id) {
var data = $("#grid1").jqGrid('getRowData', id);
var cm = $('#grid1').jqGrid('getColProp',mycolname);// mycolname is the column you're going to enable/disable
if (data.myfield == 'Y') {
cm.editable = false;// Not Editable
} else {
cm.editable = true;// Editable
}}