Can't write to variable

Hi! I really need help with this one, i’ve tried to fix it for weeks.
Basicly I have two movieclips, one can hittest the other. But after the hittest i try to write a variable from the first movie clip to the other:

_root.tower1.mc = “hi”

Then i have a movieclip inside tower1 where i have:

trace(_parent.mc)

but i get undefined!

both movieclips are attached using attachmovieclip.

What the hell am I doing wrong? please help me