How do you do cut scenes with random units removed?

Ok, say you want to do a cut scene with just heros during a campaign, like in the game. But you pick up some units along the way. How does Blizzard remove those units temporarily and do the cinematic with only the selected heros?

If they are all Units, Im pretty sure that there is a simple trigger that targets units in a region or whatever... Not rly sure, tired as hell and dont ave Worldedit open.

I believe they pause and hide all units. You could always extract some of the campaign missions and look at the triggers.

unit group, kill picked units in xx region

That wouldn't work! Once the cut scene ends the units will all be dead. Use the hide units/unhide units triggers.