How to get GUI Handles (GUIDE) into a Level 2 Matlab S Function?

I made a Simulation in Simulink and a GUI with GUIDE. Now I am trying to get data from the simulation into the GUI during the run time of the simulation. To do so I am using a Level 2 Matlab S Function with the inputs that need to go into the GUI. To write the Data directly into the right GUI objects I want to get the GUI handles into the S Function. My Problem is that I am not quite sure how to adress the GUI in the s function code. I tried using findobj() but it seems like it does not return anything.

Thank you in advance!