Payment received

I have received a payment. It is for three items. Two invoices we have raised. Plus a further amount which is funding and no invoice was raised. I need to split it so I can "pay Bill" for the amount relating to the raised invocies and "Receive Money" for the funding portion. Can someone advise the best way to process this? I think I need to use the undeposited funds account somehow but I can not remember the process. Thank you