Round 2 is opened ......
How the h'** do I get the actual Window from my MUI-object

thought it should have been this:
struct Window *win;
DoMethod(obj,MUIA_Window,&win);
But when I try to draw something into the RPort of that window, I get massive
slowdowns and crashes. Drawing after assigning rp tp _rp(obj) does work, but this
ain't a option, sice I want to call a function which expects Window*, and doesn't
know nothing about MUI.