How can my APPX process tell if a user is running the GUI client?

Is there a way in ILF to determine what type of client the user is using to run APPX? For example, if a user is running a "text" client, we want to display a text menu. But, if the user is running a GUI client we want to display a GUI menu.

      GOSUB    --- CHECK GUI CLIENT
      IF       --- RETURN CODE        EQ     1
T     *        Running with a GUI client
F     *        Running with a character client