Creating a path in a part?

[Superslinky]

Hi all, I have a guestion. I'm trying to create a path in a part that has some pretty funky curves in it. I think if you look at the attached file you'll see what I mean but the inner part needs to be able to slide out of the back of the outer part and when in position (as shown in the assembly) the flange of the inner part seats where it's at. I'm on V19.