movie clip motion/tracking(gamedev)

I have attach a screenshot to better represent the description of my problem.

I need my "enemies" to move along the 'screw' animation in the game. So they need to move one way- dissapear, and then respawn at the next thread of the screw. My 'logical' solution was to put my enemy movie clip onto a motion guide, and the peak of each 'movement' i will swapDepths with the screw. Again the problem arises, how do i do this for 10-20 enemies at a time?

Screenshot