current customer payment status and other billing questions

[Adam Rose]

Is there a perl method already written to figure out what date the
customer is payed to.

Unlike the next bill date on /view/cust_main.cgi, I need a "payed up
to" date field. 

I am working on a payment method to pay on payment accross multiple
invoices.  I am having some difficulties though.  Should a negative
invoice exist when someone overpays or should a new invoice be generated
to allow for making an invoice "closed" the next month?  The same theory
seems to be applied to credits.  Should a credit be used to pay on an
invoice to apply towards closing out the invoice?  If not, how do you
figure how much needs to be owed on an invoice when credits are put in?
(Currently using $cust_bill->owed) 

Any help on this topic is greatly appreciated.


--Adam