I only use jQuery so thats where most of my knowledge is, but they both have enormous amounts of plugins for this sort of things. I've never used it so I can't attest to its quality, but this jQuery script seems to be very close to what you need functionality wise:
http://www.webdesigndev.com/web-deve...u-you-ever-saw (
demo)
If that one doesn't work here is a list of 38 (jQuery) dropdown scripts:
http://www.1stwebdesigner.com/css/38...enu-solutions/