Hi Pamela,
you can set a requirement formula that if it is fullfilled, output is determined when saving the sales order.
Run V/43 to find out output procedure for your sales order type
Run NACE and select application V1, click on procedure and select your output procedure you found in previous step. Click on control to display the messages included in the procedure. In column requirements is where you can set your requirement formula that you can define in tcode VOFM, requirements, output control.
Look for the help of an abapper for the coding.
Regards,
JM