More than one IC Partner Code for each Company

It would seem that it is only possible to post intercompany transactions to one “IC Partner code” for each company.
I need to be able to post to a larger range of intercompany accounts on the balance sheet.
For example, if I create 2 “IC Partner codes” for one company, this allows me to use one “IC Partner” code for Sales & Purchases journals and another for Accruals journals.
However, when I import IC transactions via the IC Inbox, the “IC Partner code” is validated by the” IC Partner code” field in the Company Information table. It is only possible to enter one IC Partner code here.
Do you know why the “IC Partner code” is validated against the “Company Information” when importing into Navision? Is there a way to amend this?