making a random value everytime i check a checkbox

There are no real buttons in expressions and I think that's where your whole plan falls apart. You seem to assume that checkboxes work this way and controls associated with them somehow store the various states they are in. This is never going to work, no matter whether it's animated or a static control. If at all I would imagine you could write some complex auxiliary expression that e.g. populates an array or stores values as strings in a text layer do you have some way of not having to recalculating everything all the time, but even do you would need another expression to fetch and convert the values back as well as having code to check whether a specific random seed isn't used twice. Once again: None of this makes any sense from the "How AE expressions work" POV and I'm pretty sure even if you could get it to work natively in AE it would still break with Essential Graphics or Dynamic Link. Sorry, but this just feels wrong on so many levels. So from where I sit a much simpler approach is needed like having two or three sliders whose combined value drives the random seed or such. This would sufficiently reduce the probability of producing the same results and you could "harden" it further by tying the seeds to the effects numerical induced as part of the formula.

Mylenium 

Not sure exactly what you're after, but it's probably going to be close to this:

cb = effect("Randomizer")("Checkbox");
val = value;
if (cb.numKeys > 0){
  for (i = cb.numKeys; i > 0; i--){
    if (cb.key(i).time <= time){
      if (cb.key(i).value){
        seedRandom(i,true);
        val = random(value);
      }
      break;
    }
  }
}
val

You need to run it in a loop and evaluate it for every frame. AE does not store persistent variables and values so despite your convoluted code the result is basically the same all the time. That and of course it makes no sense in the first place. If a slider is already involved, you'd simply keyframe that because there is no way to carry your checkbox states, either, other than e.g. counting the keyframes on it. Again, your approach just doesn't make sense.

Mylenium