Technical Guidance needed in customizing PO Account Generator for a Complex PO requirement.

Hi ,

I need to customize the PO Account Generator for the following business requirement.

1. PO Account Generator derives the accounting segments for all the distribution lines while creating a COMPLEX PURCHASE ORDER (Complex PO).

2. Workflow defaults PO charge account for all the distribution lines.

3. There is provision to enter advance amount in complex PO while creating.

4. If there is any advance amount entered, a new distribution line will be there with name (Advance- **) and accounting segments(Charge accounts) are derived/defaulted  for this distribution line also.

5. My business requirement is to derive and default the prepayment accounting segments defined at operating unit level (Financial options) instead of PO charge account (derived by workflow as a standard process).