Changing This Code To A Function? (how Do You Make Functions?)

I have a menu system that has nodes that can be opened or closed. In an
effort to make my code more manageable, I programmed a little widget tonight
that keeps track of the open/active item and automatically builds
querystrings for my redirect URLS. The code for this follows. It defines an
ASP Dictionary object, and key/value pairs for each, and builds appropriate
querystrings based on comparison with a status variable.

The way it works for now is I manually declare and re-declare a variable
("CurrentContentClass") in places throughout the code where there is a new
menu item. I embed this same block of code repeatedly through my
application, one for each menu node. This is a really stupid approach, and
I'm sure there's a better way.

Better would be to create a single function into which you could feed
parameters and get output. I've used lots of functions in my auspicious
career in ASP, but I've never created one myself.

Can anyone suggest tutorials or approaches such that I can learn how to
create my own functions? Any guidance based on what's below? Code: