@Eliot:
yes, the Intuition/MUI discussion is really irrelevant and I've been trying to focus this thread back to my real problem. :)

What do you mean exactly ? How would you start the engine from the GUI then ? Execute() doesn't seem to be interactive, more like a "fire and forget" function. What would you use ? RunCommand() ? CreateNewProc maybe ? Sorry for the naive questions, I'm really a beginner hone it comes to Amiga system programming. :)

I've taken a look at SystemTagList() and it looks quite complex to use. Also I've read on a forum (maybe incorrectly ?) that it'll open a wheel window, when what I want to do has to be invisible to the user. I read this here, from someone who obviously was trying to solve the same problem :
http://aros-exec.org/modules/newbb/viewtopic.php?start=0&topic_id=7987&viewmode=flat&order=ASC&type=&mode=0