Ok I've started working on the shield type covering on the arm still more work to do but a few questions

Below is a picture with one part circled in read, that part will be the piece on the side that will hide the arm inside
The part in yellow is what it will look like once the arm is out of the flash drive and in action (still not done placing the items.



roughly where the arm will be placed inside:



Now the couple questions
The part circled in red will not be the part that is actually attached to the arm because of the way the arm sits in there it wont work right being attached to the arm. But as the arm is pushed out in the animation as a piece starts showing that's attached to the arm I want to make the outside piece actually just disappear, almost like it is attached to the arm. How do I make the pieces of that vanish as the pieces attached to the arm in yellow start showing when the arm is popping out of the side? Is there a way to do this? Should I still be thinking of using Set Driven Keys for the arm coming out? Can I use set driven keys to make the pieces disappear from the outside?
Or maybe with the set driven keys the part from the outside will move into place as the arm is moving out and I shouldn't have the part in yellow pre-placed?

Any help with this and I would greatly appreciate it.

If you need to to clarify any of this any better just ask and I will do my best.

Sorry to ramble like that. Just trying to get it all out in one post without having to make 5 posts just to ask the one question

Thanks for all the help so far to