var cart = container.getComponent('Cart');
			var data = {
				fieldId: "custbody_customerref",
				type: "string",
				value: "C123456"
			}
					cart.setTransactionBodyField(data).then(function() {
					console.log(data.fieldId + ' was set to ' + data.value);
				}).fail(function(error) {
					console.log('setTransactionBodyField failed.');
				});