I am trying to convert a Purchase Order to a Vendor Bill and control which line items and which quantities are being billed, however I'm getting 2 errors... I'll start with one though. When I want a partial bill, I want to delete a line item right? But when I try

vendorBill.removeLine({ sublistId: 'item', line: i });

I get the following error message:

You have attempted an invalid sublist or line item operation. You are either trying to access a field on a non-existent line or you are trying to add or remove lines from a static sublist.

What is going wrong?? Also

vendorBill

is loaded in dynamic mode