Hi Rusheek,
This is very weird requirement and can not be achieved using any configuration or authorization. You will have to code it for which you have multiple options.
One easy thing you can do is
1. provide create/change authorization to the users
2. implement ORDER_SAVE BADI in which you can put a check on channel (GUI or Web UI) and raise DO_NOT_SAVE exception by giving the desired error message when channel is GUI.