How do I sort z by y?

I have an ai following me and another ai following the first ai. I want them to sort themself properly so it doesn't look like the one in the front is under the one at the back.

I tried to do this but I just can't get it to work even though the event should be right following the advice that was given in this thread?

link:

https://www.scirra.com/forum/z-order-equals-to-y-position_t85622[/code:1df5mcm1]

my code:
[img="http://i.imgur.com/r8mHcTv.png"]

I guess you could use:

for each crew ordered by crew.y descending

• crew move to bottom of layer..

Thanks!