[Samba] Invoice numbering for customers

[subscriptions]

Just wanted to ask a quick question here. I am running GNUC 2.6.12 and 
when I create a invoice for a customer I have to enter an invoice 
number. I was thinking perhaps there is setting somewhere that I missed 
to get it to automatically fill in a invoice number? Id hate to have 
invoices with the same invoice number since I have to manually type them 
in right now.

Thank you,

jdegraw