Create/Update supplier bank accounts for existing suppliers/sites using api's/ open interface?

In R12, how do you update/create the supplier bank accounts for existing supplier and supplier site using interface/api's ? 

Is it correct that the bank account details cannot be imported individually and it can only be imported along with the supplier or supplier site? Please provide the steps if we can update the bank account details (like the import program and all that?)

Thanks in advance!