Enter commission on inter-bank transfers

The Sage200 documentation says that on an inter-bank transfer you can enter the value of any commission charged. This is NOT TRUE. It appears you can only enter 'commission' on a transaction between banks of different currencies - which is in fact a form of exchange rate difference. Our customer uses factoring for some of their sales receipts. When they submit the list of invoices to be factored to the agency, they are recorded as having been 'paid' in the sales ledger by a bank account specifically for the factoring agency. When the factoring agency pays the company, they deduct a commission - but this commission cannot be recorded as part of the inter-bank transfer. Commission is NOT dependent upon foreign exchange transactions. Our customer operate factoring in both euros as well as sterling, as well as having bank accounts in euros, sterling and dollars - and have 'bank accounts' for monies due / expected from American Express and other card companies. This is not really just an idea - it is a business issue that needs fixing.