Restrict Systems in Landscape block in Normal Change(CHARMS)

Hello SME's,

I got one situation.My CHARM project contains two different landscape so whenever a Normal Change is raised, In Landscape block in Change Document it is showing systems of both Landscape while in urgent change It is showing systems of one landscape.So my requirement is like I want systems of one landscape at a time in my CD so how we can control it.?

I require this because below is my charm landcape:

Charm Landscape is like  ABD100 - ABQ100 - ABP 100

                                      ABD200 - ABQ200 - ABP 200

So when user creates TR he is not checking whether the TR is getting created in 100 or 200 client which creates a mess so Is there any way in Normal change we can restrict the systems means only one landscape should come like 100 or 200 at a time.Please suggest some solution.

Regards,

Abhishek