Sales Order/Invoice Auto Generation

Hi Guys/Gals

A little background into what I am trying to do.

I'm working on a script that runs from a customer record. When it runs I would like it to check a search and returning a set number of records. I have this working perfectly. The next part (the part im struggling with) needs to generate an Invoice based on these returned records.

I have tried the following (which works fine for purchase orders), but i get an undefined error.

    var record = nlapiCreateRecord('invoice');     record.setFieldValue('entity', compid );       record.setLineItemValue('item', 'item', 1, 13);       record.setLineItemValue('item', 'quantity', 1, 1);       record.setLineItemValue('item', 'rate', 1, 21);                            var id = nlapiSubmitRecord(record, true);