Restricting the Discount percentage

Hi All,

Need your help in the following senario ,

for discounts to customers or material,

enduser can enter only upto 5%,

if it is more than 5% the order should be saved but it has to be blocked

and only manager can release that for further processing.

and sales manager can give more than 5% Discount.

Thanks in advance

Siva Narayana