Did you add your parameters to the widget (the slider) and then set the states for each snapshot of the slider (the balls at the ends and any other you add). If you don't set your snapshot states, then dragging the slider won't do anything.
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Mark Spencer
Freelance Producer/Editor/Motion Graphics Artist
Apple-certified Master Trainer
Author, Motion 4 from Peachpit Press
http://www.applemotion.net