Anyone Able To Help Me Successfully Use A Vocoder Plugin?

Hey folks!
I've been tinkering in the newest version of Garage Band, GB version 6.5 and Amadeus Pro trying to get a vocoder to work but so far I'm failing completely in every one of these apps.
I have three different vocoder plugins so far, two are VST and one is AU. In most cases I can find the plugin, put the vocals on the left and the synth on the right but I can't figure out how to actually use the plugin to put them together to get anything to work.
I was shooting for the Daft Punk sort of sound at first but as of now I just want to get it to work. If anyone has ideas on what to try I'm all ears! Surely there's got to be someone out there that's got the hang of this!
Thanks everyone!