SAP SD SALES ORDER WITH Mis. Fees

Hi Guru

Please find my requirement below:

1. we need to create a Sales Order with single line item.This sales order need to be created by some other upstream system through RFC.
2. Here we are using some miscellaneous fees which should tie with this SKU. So when this order comes in SAP that miscellaneous fees also pop up in second line item.
3. Third requirement is that we can add or delete that second line item in SAP.

Please advice me.Tons of thanks in advance.

Nick