How do I make a batch file have a chance to do the next step? Answered

I want to create a batch that when opened, has a 1/6 chance to open a file, if not it has a 1/5 chance to open something else, same process until final 100% option. How would I do this in batch, and if I can't do it in batch, where could I do this?
Thanks for the help in advance.