— Games What you are trying to determine is a Bayes decision tree, assuming that your probabilities are independent, Joannak is right, you should multiple them. You can't have a probability over 100% at anytime, because that would happen all the time. (So, no probabilities like 125%)
Instead of checking for each probability, build a decision tree that gives you the path for each case. With that, you will be able to determine the probability for each scenario.
Note that the sum of all the probabilities should be equal to 1 (or 100%).
A quick google search for Bayes Decision tree should help you to understand the probabilities behind of what you are doing, look for an example with numbers... Once you get the idea of it, you should be able to implement it with a function that generates a result if your probability is between certain values.
Edit: I didn't notice that the solution was already there. Yes a function will help you avoid that. Anyways, a decision tree always help in this scenario (I like graphics).