You ask:
I know the Mean return and Volatility, for some stock, and would like to know the probability that, in umpteen months,
the stock will exceed $something or maybe lie between $something and $something-else or maybe ...

>Yeah, so?

    So here's a spreadsheet which could be useful, especially if you're paying playing with option spreads, like:

   

... or Ratio Writing.

Just RIGHT-click on the picture and Save Target to download a .ZIP'd file.

>And you believe this stuff, eh?
Well, I can choose either a Normal or Lognormal distribution of stock returns and pick different time periods and ...

>And you believe this stuff, eh?
Uh ... no, but it's fun ain't it?

>No.