Slightly OT: Adding PO items to MM invoice from workflow

[Mike Pokraka]

Hi all,

Apologies for the slightly off-topic nature of the post, but after 
wrestling with this on and off for months we are clutching at straws 
that someone may have implemented something similar.

The scenario is MM Inovice Verification, workflow goes to users to pick 
PO's and items to go onto an invoice. Users do not have MIR4 access, so 
WF pops up a list to let users pick the PO's & items for the invoice.

The question/problem is how to add items onto a PO in background? We've 
gone through BADIs', BAPI's, OSS, SDN and various SAP sites, messed 
about with MRM_* function modules (chaos!), at last resorting to writing 
a BDC (ugh) which uses MIR4 - but only works for up to 8 items (there's 
no page down in the PO selection popup from MIR4).

Has anyone implemented something to add more than 8 items onto a MM 
Invoice? Is there a secret function module or other hack to do this?

Any input appreciated,
Cheers
Mike