selection screen issue

Hello, I want to restrict the list of selections in my variable. I have 0 material interval variable on my report's selection screen. I've restricted another fields called material type to a specific type called ZMT by hard coding in the query.

This is what I want. When selection screen comes up and user clicks on 0material list of values, I want him to see only materials with material type ZMT. Can you please tell me how to do that?

Thanks.