Net terms discounting

Has anyone tried to do net terms discounting? The idea is that you charge the standard price, but on the receipt you show that if they pay on their account within 30 days, that they will get the purchase at the discounted rate. Control of what can get discounted is handled with the item properties tab item can be discounted at POS. Discount is 10%. My thought was to write an add in that would calculate a secondary subtotal each time an item is added, after checking wether the item was discountable. Then to print that extra subtotal on the bottom. At this point, they would then have to do a manual adjustment on the account to take the discount off or take payment on the account in the formof a tender called net term discount. I think I should just use the event hooks for when items are added or changed and then just have the output show if the payment type is to account. I assume this can't all be done on the receipt format as I didn't see that it could put values into variables. Does this all make sense and am I moving in the right direction? Is there anywhere I can get advice on this. As certified partners I thought we could get free advice, for trying to become ISV's, but I couldn't find anything on partnersource and RMS is not included in MSDN I believe so I don't know that I can use my support from there. Any help would be appreciated, and if anyone has already done this, I would love to either buy it or get help. Thanks Tom