discount on voucher header without using payment terms option

Hello,

Could you please tell me if it is possible , in PeopleSoft 9.1 , the following scenario :

My customer wants to know if it is possible to enter discounts manually on Voucher header without using the payment terms with discount  and if it is possible to  define the discount at the Voucher header level manually.

For example, they  have 3 lines in the voucher.The requirement is to define the discount as the header level manually. So let us say, user will input 10% discount at the header level. Then all of the 3 lines in the voucher will have the 10% discount automatically.

Best regards,