Entering A Payment And Seeing A New Balance

I would like to be able to choose a month (from a drop down menu), then choose who the payment will go to ie. creditor (from a drop down menu) ie. car, truck, cc payment, as a result of those selections, then enter the amount of the payment, and finally the ending balance will appear. I have the drop down menus in place and I have all the balance calculations in place. I could use the spreadsheet that I have but I only want to see the below info. Plus I don't know how to link or lookup this data to the stuff I've already created.

Select Month:
Select Creditor:
Enter Payment:
New Balance:

I have already set the sheet up calculating the balances after a payment has been made. I know how to hide all the formulas, but I don't know how to get it to so that you choose a month, then creditor type (from drop down menus), and payment so that you see a new balance. I only want to be able to link or lookup the month, creditor together so that a payment can be made to that cell that I've already established. As a result, then that cell can be shown in the new balance.