Calling Method from Setup Script

Hi,
I have in my project a test suite, in this test suite i want to implement a method which i can call from different test steps in their setup script.
I implemented the method in the setup script of the test suite and call it from the other script but it does not work.
Groovy scripts are only available in test cases and then it is not possible just to implement a method. If I try this, an error occurs.
So I think that it is not possible in the way I am trying it.
Hope you can help me and tell a way to work around.