Referring to MC "tile + i"

I know this is quite simple and I am sure someone knows the answer to this easy problem. I am using the x.attachMovie() function. I am making a map program, and I want movieClips to be moved from their original position. I was thinking of using “tile._x” script, but since it is not simply “tile”, it is “tile + i”, how would I refer to it to move the _x, _y property?

Thanks.