Calculating Probability help needed

Hi guys,

This is my first post. Here's what I want to do:

I have 2 numbers, 1 and -1, from A1-A500, just as an example. I want to know what is the probability of a -1 occurring after a 1. Or the probability of a 1 occurring after a -1 or even probability of a 1 occurring after two -1s. I hope I worded my question correctly. I have attachd a file in case someone wants to work with it



Thanks :-)