I want to use hitTestObject on all instances of a movieclip

Hi, I’m trying to make a simple maze game. I have movement working, and now I’m trying to implement collision. Here’s what I have:

An 8x8 grid, with walls of length 1 to break the grid up into a maze.
the walls are instances of a movieclip I’ve named “mc_wall”
a guitar-pick-shaped chip I’ll control the movement of
a cross-hair called “arms” that will check if there are walls immediately surrounding my chip by way of collision.
“arms” is a movieclip made up of four individual movieclips: “uparm”, “leftarm”, “rightarm”, and “downarm”

I have currently named each instance of “mc_wall” to be “wall”
this is the code I have now (using only right as an example):

function moveRobot(event:KeyboardEvent):void
{
doslide = true;
if (event.keyCode == Keyboard.RIGHT)
{
if (arms.getChildByName(“rightarm”).hitTestObject(wal l) == true)
{
doslide = false;
}
}

    if(doslide == true)
    {
         slide = new Tween(robot, "x", None.easeNone, chip.x, chip.x + 30, 0.5, true);
         arms.x = arms.x + 30;
    }

}

this will work, causing the chip to remain in place if the rightarm detects “wall”, and move if the rightarm does not detect “wall”.
My problem is that, although I have named every instance of “mc_wall” to be “wall”, the only “wall” flash will recognize is the last one.

Is there a way to adjust this code to look at all 70-or-so instances of “mc_wall” instead of only the last one?