How to capture a piece of info and pass it later

I am pretty new to VUGEN and need to create a script.  However, the site I am trying to script  generates an unique refid for each request, so I need to capture the refid the first time I encounter it and then variablize it and pass it back to the server later in my script. 

Are there any good examples or tutorials out there on how to do something similiar?

thanks in advance!

- Alex