Run a different Test Case depending on User Input Using Selenium

I'm wondering if there's a way to run a specific test case, depending on end-user input (into a prompt window)

I will take any solution or answer that results in something similar to what I described however I would prefer it if I could run one test case OR the other. If/Else statement correct? Not necessarily running one first, then the next in line. Also if you could elaborate on a solution you've provided rather than; "Here's what works for me," copy/paste," I'd greatly appreciate it.

Essentially both test cases contain the same variables except the definition of each changes depending on conditions recognized by the end-user. Btw I'm using Selenium 2.8.0