Coordinates of mc on stage

I can’t believe I can’t figure this out! What I need is really simple, but I am obviously doing it wrong.

I have a whole stack of tile instances arranged in a grid on the stage. Each mc has a button in it. All I want is when the user clicks the ‘mc’, to return the coordinates of that mc relative to the main stage. I’ve tried _root, _parent … everything.

Does each tile have to be named? Of course I have been able to find the coordinate if I name them all but I’m dealing with about 600 of them. Also, they are arranged in a weird way that I can’t use AS to generate it at runtime. Check out the attachment and you will see what I mean.

Thanks a million for any help.

Marty