Checking mc's based on x and y cords

I have a series of mc’s that are in a grid position and another set on top. I want to move the ones on top to different positions over the others but I want to check to see if one is already there. I dont’ want to use hitTest, it doesn’t work for what I want to do. I want to position my top mc’s base on the x and y positions of the bottom mc’s. How do I check a mc for a value if all my names start the same, i.e. mc_ and end in numbers that represent their position, i.e. mc_12070. I was thinking something like:

newY = this._y - 50;
newX = this._x;

but how would I call the clip?

what is the syntax to make that work?

Any help is greatly appreciated. Thank you.