Restricting Traget Client Option When Transporting

Hi All

I have a question regarding to TMS..

Currently I am trying to find the way to restricting the target client option when I transport object to Production system.

Let's say, there is Production system and I want to transport an object to client 400.

When I set or schedule transport by STMS, I can still input any client number in Import Transport Request window

(I can put 200 or 300, even thought client 200 and 300 are not exist in the production system).

In order to prevent inputting wrong client number mistakenly, I want to restrict target client option only 400 available.

If there is any good way, could you please help me?

Thank you so much.