A simple script for Up/Over/Down buttons?

Hi folks, wonder if you can help me.

I'm a total web newbie using Dreamweaver 2 to make a homepage. I've figured
out the Rollover Image option to make buttons - all very straightforward.
But what I really want is the ability to have a 'button down' image to show
that a link has been clicked.

I've looked up how to do this and a lot of sites say I just need to insert a
Navigation Bar from the object menu, but I don't have this option in DW2. I
guess therefore I need a little javascipt to achieve this? Is this correct?
Does anyone have a 'standard' script I can use, where I can just replace the
image names as appropriate? How else can I get round this? All I have is
DW2.

TIA