Voucher Number in new posting period

hello,

I have created new posting period and series for financial year 2011-12.

In previous year I have created 600 voucher. My issue is that when I am creating new

voucher, voucher number is showing 601. I want that for new series voucher number should be

start from 1. but it seems like numbering series doesn't affect the voucher number.

Because there are no series creation for journal voucher. In this case how can I solve my problem.

Please help me on this.

thanks

Annu