Can Marines and/or Stealers use some of their action points, then shift to another model, use some of their actions. And then return to the first model?

For example. Say I have four genestealers in a single width corridor.

At the end of the corridor, 3 spaces from my front genestealer, is a marine on overwatch. Could I move my first genestealer forward, hopefully survive the overwatch fire, and then shift the two other genestealers up behind him. Then go back to the front genestealer, move him one more space forward (surviving the over-watch fire for another round hopefully!) and then move the other 2 genestealers up as well?

I don't see anything about finishing all your action points before moving on to the next model

Any rulings?

Interrogator-Chaplain Severus