balance forward billing: able to set starting consolidated bill number?

Summary:

1. envs seem to start from low number such as 1, then without much use suddenly increase (i've seen, 2 then 1000, without any apparent activity in between)
2. context for question of setting start number is: some outstanding invoices in r12 are already consolidated, but the load of invoices can't accomodate the prior consol bill number. to 'contain/identify' the invoices with 'old system consolidation' we plan to do a initial Create Balance Forward Bills, and after would like to set the consol bill number to a distinctive value that doesn't overlap with those used in the old system. reason is that when customers with those old BFB numbers pay/enquire, the difference in numbering will readily identify whether they are referring to old system number or new system number