Print only one copy of Billing Document

Hi:

I have a problem printing bills documents.  We need sometimes to print only one copy of the bill instead of all copies, using Tx. VF31 or VF03.

We have set up the number of copies of the billing in Sales order, so when printing  from these transactions always print all copies.  So I don´t know how to indicate the printing program that we only one copy (it’s Z).

Do you know if there is a way to print only one copy? Using a user-exit? Ideas, please.

Thanks in advance for your time.

Best regards.