Discount should be provided in Billing

Hi Experts,

              I have one requirement,We have Dealers and Stockiest

1)Dealers will get 1% Cash discount if payment is available in their G/l account at the time of invoicing for the invoice value.

2)Stockiest will get 1.25% Cash discount if payment is available in G/l account at the time of invoicing for the invoice value.

Please help how to do?

Thanks

Rakesh