Can we calculate number of line items in a transaction using saved search?

I am doing the below on a Item Fulfillment UE.

function beforeLoad(context) {
            var newRecord = context.newRecord;
            var numLines = newRecord.getLineCount({sublistId: 'item'});
            log.debug({title: 'Number of Lines', details: numLines});
            // add field via scripting // will show the number of lines on the fulfillment record.
            var form = context.form;
            var field = form.addField({id: 'custpage_num_lines', type: serverWidget.FieldType.TEXT, label: 'Number of Lines'});
            field.defaultValue = numLines.toString();
            field.updateDisplayType({displayType: serverWidget.FieldDisplayType.INLINE});
        }