Cash Discount Check Box for Material in Pricing!!

Hello Experts,

We have a Check Box for Cash Discount in a Material Master in Sales: sales org 1 tab.

This is used in pricing requirement 014. Now if in Material Master it is not checked it will not pick the Cash Discount from Payment Terms. But by mistake in Material Master this check was not there and so the Invoice is created without Cash Discount. Now can we correct this? If yes, how? Even if we cancel the Invoice, this field in VF01 is gray field so we cant change it. May be, if we cancel the Invoice and if we can change this check box in sales order, it would be possible to flow the same in Invoice. But where can we see this field in Sales Order?

Quick reply would be appriciated.

Thanks in advance.

Br,

hp