Okay, probably you may want to wait for some brainiac to explain it to you properly. And as I'm writing this I'm noticing mighty Ashley replying... I'll still reply anyway.
I'd say you need loops where you want certain events/actions being executed many times a tick, instead of only once.
I have uploaded a little example
for you with a WHILE loop. We have a Global there called Outcome and we want it to have the value 0,1,2 or 3, which is Random(4) of course. But we also want to be able to dynamically exclude certain possibities. We define these with the Nono_a and Nono_b globals. The values set there are values Outcome must never have. So we cannot simply run Random(4), but we run it until the result will be different from Global Nono_a+b. And all this will happen in the same tick, thanks to the while loop.
So if you run the example hit X and you will see the value will always be different from the ones defined in the Nono globals.
I hope that was some help at all... maybe this example was horribly lame.