very stupid question about lookup

Hi 
   I have implemented my own server in a module, in another module i am ok to lookup its instance by :

		for (MainService s : Lookup.getDefault().lookupAll(MainService.class)) {
			ModuleLib.log(s + " = " + s.peter());
		}

But i need to include module A in module B. That is not right i thing, because when i did that, the toolbar button (i meant the actions) from module A will crash when i install module B. Another big question is : how about they both need to lookup each other, do that need to include each other?

thanks
from Peter