Discount Transactions

How Can I make all Discounts like fixed amount,percentage etc in one transaction? I want to get all discount amounts total in one account . I trie dried to use but discount transaction used by calculation comes up . what am looking for is any kind of discount whether its percentage or amount comes to a one summarised discount amount value so that we know how much amount been discounted for . And alos how can we achieve a One Discount Button click will get few types of different discounts we can choose ? this may decrease the command buttons space.