Most likely someone has done this before and also knows how to but not for the addin you have. If the add-in is using modal window, then it will be much more difficult or impossible (not 100% sure if you could bypass modality). Below is very simple example
Names Default To Here(1);
New Window("Example",
rb = Radio Box({"single", "double", "triple"}, Show(rb << Get()))
);
wait(2); // for demo purposes
wref = Window("Example");
wref[RadioBox(1)] << Set(2, Run Script(0));
Also what do you mean by this "...and don’t have access to script"? is the add-in script encrypted?
-Jarmo