OSCOM billing and receivbles functionality

Need system to track payments made against orders. Flow would be my accountant receives a payment. He logs in to OScom and sees a screen.. and selects the client. Inputs the amount, check number, bank name and date on the check and date received. (and probably hits refresh) For this master record (client payment) a detail below shows this client's invoices which are less than 100% paid. and shows order number, order date, order amount and paid to date... and an empty field "amount to apply to this invoice from this payment" he inputs an amount here and can move down the list of pending invoices applying amounts paid. There would also be a field checking that he does not apply amounts that sum to more than the payment received. If the check amount was greater than the sum of the balances due of the invoices... there would have to be a way to handle the over payment. My thought would be to have a record for everyclient that always shows up in the details section of this form (sort of like a dummy invoice) that is called overpayment_holding. So if I have an over payment... I apply it to this dummy invoice and then when I have a new invoice I apply a negeative amount to the dummy invoice and that positive amount to the new real invoice. Now on the invoice we need to add some fields to show these payments. below the grand total on the invoice show the payments made . Date check number check amount amount applied to the invoice. and below a calculated field of Amount Pending (gand total minus payments applied) These fields will be added to the client side and admin sides invoice and also to a PDF invoice that we have added to our oscom install. (that may be 4 seperate spots) Then create a client statement report accesible from the admin - Adding two buttons one that brings up a date range prompt and filters the report on the date range. One that reports all outstanding. This client statemnt report would have all the header info from the invoice and in the detail it would have Invoicenum:invdate:invTotal:totalpaid:TotalPending with detail records below each invoice showing show the payments made . Date check number check amount amount applied to the invoice. Sum the detail records at the bottom Total invoices, Total payments , total pending I anticipate a round of questions and answere before we begin and will provide lots of communication as we progress should you have any questions along the way.