Vista - Accessing Named controls within a datatemplate

I would like to use triggers to modify items within my datatemplates .
Forinstance, I have a stackpanel that i would like to be visible ONLY if a
certain bool in my dataobject is true. Only problem is, when I try to use a
trigger, I can't seem to point to the right object. If it's a named object it
says that It can't find that object, or if im trying to use a path, well, I
think I really need to see a good demonstration of paths used within a
template. Can anyone offer some help? I concrete example of accessing a named
object within a datatemplate wouldld be great.
Can this be done in xaml? Or should I just be looking at doing codebehind.