Number range

Hi,

My requirement is to have additional number range for an invoice which will simultaneously get updated with billing document number.

I have to maintain a seperate track record for and sequence of VAT invoices i.e a number range that will start from 1 from 1 april every year.

I also want to classify this numbers as

1) VAT registered customers

2) Unregistered customers

3) Stock Tranfers.

Can one one help in this?

Regards