Requisition Import

I am importing multi-line requisitions into Purchasing from the table PO_REQUISITIONS_INTERFACE_ALL via the Requisition Import concurrent request.  In some situations, one line of the requisition will fail to import, e.g. invalid accounting, while another line on the same requisition successfully imports.  When this happens, I can no longer import the failed line after the problem has been corrected because the requisition already exists in Purchasing (due to the successful import of the other line).  I was wondering how people have handled this situation:

1) Is there a way to import a line and add it to an existing requisition?