How do i stop a unit from moving?

[How do i stop a unit from moving?]

dostop this

or

commandstop this 

works also... but they can move if given another order by their commander

[command for everyone in an area]

I'm trying to get everyone in a list trigger to only stand up when they're in the area. I've done it before on ARMA but it was ages ago. I've got something similar to work recently but this doesnt seem to trigger at all right now...

{_x setunitpos "up"} foreach units thislist

^^ that doesn't doesn't trigger at all, I even put a hint in there to see if the trigger activates and it doesnt show. However, if I type...

{_x setunitpos "up"} foreach units group opfor_group1

it triggers and they all only stand up.

Thanks in advance.