GnuCash questions

[Jon]

I am using GnuCash to do some basic business invoicing, however I can't 
seem to get the type of invoicing structure that I am accustomed too and 
would like to use. Is there a way to do this and what would be the best 
way?

I would like the invoice to show a total project amount but only bill a 
variable percentage of that amount per invoice. Show paid amounts and 
due amounts with a running total.


For example:
$10,000.00 total project I have invoiced 15% of the project and received 
the invoiced amount, next month I want to bill 20% but want to invoice 
to show the running log

Total Fee               Billed         Date            Credit/ Debit
$10,000                 15%          01/01/09         $1,500
                               Paid          01/30/09       -$1,500
_                               20%          02/01/09        $2,000_
                 % Billed  35%         Total Due       $2,000      

Hopefully that is clear, I am sure there is a better format, but I am 
still working on it.

Thank you for any help.

Jon Hyams