How Can I set an Error Msg?

Hi Sappers,

While i am doing release order with reference ro a qty contract, if i change order qrder qty mannually more than the contract quantity, It allows me by just throuing a warning msg. How Can I put error message the if quantity exceeds?

I set my cust master record for Max partial deliveries as 2,

while doing delivery, it allows me do partial delivery how many I want.

How can set Max partial Deliveries with an error Message

Thank you