Sales Orders Process Constraints

Hello

I have the following business requirement.

Once the sale Order is Booked and the líneas has been shipped no one can change or add lines .

Thanks for your help

Here you are the custom messages that I need :

"No one can add a line to an order after any of the lines on the order have been invoice interface"

"Only the customer service manager can changethe discount percentage on a order line after the line has been shipped"

"You must provide a reason if you want to cancel an order line after it has been booked.

Best Regards