如何在watir中自动化网页？

I am using Ruby with Watir to open irctc webpage. I can enter username and password automatically. When It comes to CAPTCHA, I can not use any syntax to enter a CAPTCHA. Because I do not know what it will be beforehand. I just want a simple method in which I can enter CAPTCHA by hand. While entering CAPTCHA my script should wait, then It should execute next syntax from script.I am using Ruby with Watir to open irctc webpag