We had a FileMaker developer build a workaround for us.  Purchase orders and item receipts are done through QBE.  Payables are created through the FileMaker interface which correctly links everything in the back end.  The payable can then be edited in QBE.  We've just finally implemented this into our workflow in the last couple weeks.
Send me a PM if you want more info.  I can chat with her, she may have interest in sharing, which might save us some of the development costs.