How to Align To an object but disregard the rotation?

So I'm making an animated video, I've got a generic stick figure, and I want him to be doing a Shakespeare play, holding a skull and moving his hand up and down. So I figured I'd use the Align To Behavior and connect it to the arm. I've done that, but the arm is angled, and I'm rotating it on it's anchor point to make it look like it's going up and down. And the skull is angled the same way as the arm. I can't seem to find an easy way to keep the skull attached to the hand and still remain connected to the hand while I rotate the arm, but not have the skill tilting left or right (rotation). I only want the X and Y axis to move. I've attached a video so you can see what I'm talking about.

It look a lot like rigging in 3-D animation software. Can you create a hot point or center point for the skull on which it can rotate?

I would have put the hand and skull in a group together, and linked that to the arm. The skull I believe you're simply going to have to manually keyframe its rotation.

I have never tried to create parent and child objects with motion. If Motion can make use of inverse kinematics and forward dynamics you are golden.

UPDATE: Easy! Use a Link behavior on the Skull's Rotation Z parameter.

I grouped the arm and skull together and rotated the group, so they're attached at all times, and readjust the anchor point to the required pivot location.

Then Link to the Group's Rotation Z parameter, and used a Scale value of -1.

I did a short video up about this, hope it helps.

step #1
put all elements (arm, skull) into position, set anchor point of arm



step #2
apply MATCH MOVE behavior to skull (here: rectangle


… no step 3… 

Ahh! That worked! Idk why I was doing Align To. The title made more sense in my mind for some reason, but this is exactly what I needed. Thanks!!!