unbilled receivables

  I am working the Korea implementation and I am very preplexed over trying to figure out how to set up what they want.

Here's what they have asked for:

OM to AR interface (essentially a sales invoice) would produce the following entries:

Dr. Unbilled AR

    Cr. Revenue

At the end of the month they produce a manual Tax Invoice which should produce the following entries (This is the invoice the customer pays from).

Dr. Billed AR

    Cr. Unbilled AR

I have been playing around with accounting and invoicing rules but can't seem to get it to work.

I thought having an invoice rule = Bill in Arrears and an accounting rule - immediate would do it but no luck.