Getting customer deposits from a "V" table is there a way?

Hello again I have a few questions regarding getting Customer Deposits.

Currently I have to create a "prforma" report with customer deposits. Problem is that with the data given to me Billing Doc. Number, Cust. Number, etc. etc. I am getting data from VBRK, VBFA, VBAK, ... and other assorted sales and billing tables.

My question is with the data given to me whats the fastest and best way to get the customer deposit for each profrma/billing number?

I tried Zuonr but the problem with this is that the place I work for has no standard regarding what to input here.

The way I see it, I can get it using BSEG (inputing BELNR, Fiscal Year, Company Code, Customer Number, XBLNR, and amount) then using BKPF get BELNR, and the billing date from VBRK. Im not sure how efficient this is though, or how even effective this is.

Hope I get some replies soon take care guys.