How to avoid duplicated random values?

So my initial thread got ignored (probably due to the fact that it was erroneously posted as a 'Discussion' and not a 'Question'), and the title question here was probably badly phrased. But let's try this again anyway, because I'm now at the point where I can't move forward until this is DONE.

How do I avoid this:

(set: $hss1_r to (either: 1, 2, 3, 4, 5, 6, 7, 8))
(set: $hss2_r to (either: 1, 2, 3, 4, 5, 6, 7, 8))
(set: $hss3_r to (either: 1, 2, 3, 4, 5, 6, 7, 8))
(set: $hss4_r to (either: 1, 2, 3, 4, 5, 6, 7, 8))
(set: $hssh_r to (either: 1, 2, 3, 4, 5, 6, 7, 8))

...giving me a set of numbers like this: 1,1,4,5,4

The point here is to send five 'kids' (hss1, hss2, hss3, hss4, and hssh) to different rooms, of which there are 8 to chose from.

I cannot have two kids in the same room. So while the formula for hss1 can pick from any of the 8 rooms, if it draws 4, how do I keep the others from drawing 4, and so on?

I was hoping to have Chapter 4 done already, but until I work out the hide'n'seek mini-game this set is meant to kick-start, I can't publish and unleash my testers on it. I've been stuck on this for two weeks now and would appreciate any help at all.